The paper， using overlapping generations model， studies the impact of migration friction on the long-term dynamic evolution process of rural-urban migration． It shows that migration costs， the urban unemployment insurance， and search matching friction shape the basic characteristics of rural-urban migration if there is segmentation in Chinese labor market． The rural migrations will adjust the investment in education rationally when migration friction changes． The quantities of technical workers will be more sensitive to the changes of migration friction because education investment is a concave function and migration labor is risk averse． The more sensitive changes in the quantity og technical workers will lead to the more sensitive changes in salary， and the riddle of migration may result． Improving the housing and medical insurance of migrants and labour market mechanism will reduce the migration cost， raise employment probability of temporary workers， and will accelerate China’s urban-rural migration and be an effective policy to solve the riddle of migration in China．