The horizontal development of world history refers to the objective process of history from mutual occlusion to gradual opening, from mutual dispersion to gradual close contact, and finally to the whole world history. In prehistoric times, human beings in primitive state lived in every corner of the earth in clans, tribes or villages. Although archaeologists have proved in kind that these scattered points are not completely isolated and isolated from each other, and there have been some accidental contacts, because of the extremely low level of material production at that time, it is impossible to have too much division of labor, too much exchange and communication between the points, and even less to have too much room for pioneering activities. Therefore, points are basically closed to each other, and there is almost no horizontal connection, which is extremely limited. After entering agriculture and animal husbandry, with the development of material productivity and the formation of private property, class society appeared in some areas. This broke through the extremely narrow isolation of primitive clans and tribes and began to form a country with a certain range of fields. There are also more exchanges between countries and regions, including peaceful and violent exchanges. But in the pre-capitalist stage of class society, even the agricultural areas with relatively developed economic development are basically self-sufficient economies. Although the social division of labor and exchange has developed, it is limited after all, and handicrafts and commerce are still in a subsidiary and supplementary position. As long as production is not beyond the scope of natural economy, the state of relative isolation among all ethnic groups, countries and regions still exists. 15 and 16 centuries, capitalism sprouted and grew in western Europe. With the "geographical discovery", the overseas colonial expansion of western countries and the formation of the world market, the long-standing closed-door state among countries, regions and nations has been increasingly broken, and the whole world has gradually formed a closely linked, interdependent and contradictory whole in economy, politics and culture. The decisive force to push history from various points of primitive human scattered life to the final world is also the continuous development of material production. On the basis of the continuous development of material production, people's exploration of new fields and exchanges and contacts with surrounding areas will inevitably continue to expand. This expansion will inevitably lead to a breakthrough in mutual occlusion, a process of gradual breakthrough in mutual occlusion, that is, a process in which history gradually develops into world history. Although the degree and order of breaking the closed state in different regions and different stages of development are not consistent, the horizontal development process of history still has universal significance in theory.