In this research, the spatial distribution of migration and its major reasons in China during 1985-1990 at the county level was analyzed based on 1% original data of the Census 1990. As a result the following facts were clarified. Firstly, the migrants were absorbed to the developed and developing cities such as the municipalities under direct control of the Central Government, capitals of provinces, and regions where the Reform and Open-door Policy was carried out at very early stages (Shenzhen, Guangzhou, Baoan, Dongguan and so on) from their surrounding areas. Secondly, the number of intra-province migrants, which occupied near 70% of the total migrants, was much more than that of inter-province migrants. The destinations of intra-province migrants were the capital of province, mine lots, big cities, as well as regions where the Reform and Open-door Policy was carried out firstly. The destinations of inter-province migrants were mainly located in the cities and surrounding areas of Beijing, Tianjin, Shanghai and Zhujiang River Delta. Thirdly, the number of Non-hukou migrants (movers who did not change their household residence registration) occupied near 50% of total migrants, though it is less than Hukou migrants (movers who did change their household residence registration). About 80% of Non-hukou migrants are from rural areas and about 50% of Hukou migrants are from urban areas. Almost 70% of the Hukou migrants are students who migrate into upper-grade administrative districts for the entrance of universities or specialized schools, and professionals who migrate for job transfer. More than half of the Non-hukou migrants were workers, who move for economical purpose and engage to the factories for spinning and weaving industry, processing industry and so on. Finally, economic development condition, especially the economic scale, was closely related with the in-migrants, which can be considered as the most important pulling factor. In addition, a simple regression model to calculate the number of in-migrants of all countries by GDP was suggested.