Based on the general description of the in-situ urbanization process of farmers in Beijing,the paper provides a specific case of the participation in city construction using the collective land in Dongsheng Science and Technology Park of Haidian District.It presents that the mode of in-situ urbanization in Beijing solved the three contradictions:the contradiction of urban-rural dual structure of the system,the contradiction between farmers and collectivity,the contradiction of reform and legal system.At last,this paper puts forward the mechanism design and path selection for the in-situ urbanization which let farmers get the benefit of "the industry,the assets,the social security and the organization". <<