Abstract: The Peasant- is a special group coming into being in the course of gradual establishment of the socialist market economy system and promoting urbanization greatly. Because of profession and identification, peasant workers have many their own features in quantity、employment、income、social security ,etc.. At present, due to serious backwardness of social security, many livelihood problems in which peasant-s' medical security is an important one have been integrated into legal system adjustment fields. Central and local governments have payed high attention on the issue of peasant-s' medical security and are trying hard to explore and take various measures to solve it. Based on the investigation of the present situation of peasant-s' medical security, discussion on the construction of legal system of peasant-s' medical security has significant value and practical meaning to perfect social medical security system with Chinese characteristic and secure sound and rapid development of urbanization of China.