Through historical literature study，this paper finds that there are different connotations of the Cooperative between the New-style Rural Cooperative Medical Scheme （NRCMS） and the traditional one，the traditional cooperative medical scheme doesn’t belong to social security system while the NRCMS not only has the basic features of social security，but also has the relatively mature elements of social security，such as the playing of government’s leading role，the design of social security parameters， the implementation of the law of large numbers，the principle of the combination of rights and obligation and actual mandatory. The clarification of social security features of the NRCMS is helpful to control the “reverse selection” brought by voluntarily participating in the NRCMS，promotes the seamless connection between urban and rural basic medical insurance system，and speeds up the definition of the boundary of government’s responsibility. Thus，China should develop the NRCMS towards compulsory basic medical insurance system and meanwhile change the governmental quota financial subsidy to the subsidy according to a proportion.