Second, complex ethnic relations. The frequent flow of ethnic groups from south to north and from east to west in neighboring border areas leads to complex ethnic composition, accelerated ethnic integration (natural integration and forced integration, that is, war), fierce ethnic wars and rapid ethnic replacement. The protagonists in the northern region are the "five Hu" who entered the country and the Han nationality who stayed at home. At the same time that the whole north is "Hu Hua", many difficult and tortuous Hu people are gradually "China"; In the south, it is especially manifested in the natural and compulsory integration of the northern Han nationality and the southern Han nationality who retreated to the south, as well as the more barbaric and vulgar ethnic groups. This is also a kind of "sinicization". If we consider the surrounding ethnic groups, especially the Mongolian Plateau, the Northeast and the Western Regions, the history of the Wei, Jin, Southern and Northern Dynasties is actually composed of the northern frontier ethnic groups (including Xianbei, Hu Qiang, Goguryeo, Rouran, Gaoche, Turkic, etc.) and the Central Plains region (). During this period, regional confrontation, national rise and fall, social transformation, institutional conflict and cultural integration are extremely complicated.
Third, frequent population migration. This is especially manifested in the Eastern Jin Dynasty, the Sixteen Countries and the Southern and Northern Dynasties, and the scale, scope, duration and influence of population migration exceeded any previous historical period. However, the population flow within the Sixteen Countries and the Northern Dynasties is different from that of overseas Chinese in the Eastern Jin Dynasty and the Southern Dynasties. For example, the overseas Chinese population in the Eastern Jin Dynasty and the Southern Dynasties mostly migrated voluntarily, and a large part of them became settled immigrants; The Eastern Jin and Southern Dynasties, especially the Eastern Jin, Song, Qi and Liang regimes, were essentially immigrant regimes. Therefore, overseas Chinese have a high status, great political, military and cultural influence, and receive many preferential treatments. The frequent and large-scale population movements in the Sixteen Countries and the Northern Dynasties, especially the population movements of non-ruling ethnic groups such as the Sixteen Countries and the Han nationality, were carried out by Hu rulers, mainly forced migration. They are not only in a low position, but also in a miserable situation. The purpose of Hu rulers' forced migration is to use them as soldiers and cultivate them. With the rise and fall of political power and the turmoil and chaos of the current situation, the forcibly relocated population has been repeatedly moved by different rulers, so the number of immigrants who can settle down for a long time is actually limited.
Fourth, the special social structure. During the Wei, Jin, Southern and Northern Dynasties, the development of patriarchal feudal land ownership led to the change of production relations, the door politics caused by the distribution of political and economic rights according to the family system, and the turmoil, confrontation and division caused by the violent movement of ethnic contradictions and various social contradictions, which made the four characteristics of this period particularly strong and obvious. Among them, the clan with clan and hierarchy as the core becomes the ruling class. From the Western Jin Dynasty to the Eastern Jin Dynasty, the rule of aristocratic families was constantly strengthened; Since the Southern Dynasties, although the political status of aristocratic families has declined, their social status is still very stable. In connection with this, the boundaries of aristocratic families were strict in this period. With the decline of aristocratic families, the status of common people's families gradually rose, which was manifested in the fact that the emperors in the Southern Dynasties were mostly second-class or even landlords of common people's families.
Fifth, the changing system of laws and regulations. During the Wei, Jin, Southern and Northern Dynasties, every expedient measure in the system, from the central official system to the local administrative system, was often in a transitional state, lacking a solidified system, and many systems changed at any time, from place to place, from person to person and from ethnic group. It is precisely because this is an institutional transitional era that various systems are particularly complicated. The study of China's institutional history shows that there is a great difference between the Han system and the Tang system, which is not caused overnight, but the result of natural evolution during the Wei, Jin, Southern and Northern Dynasties.