中文摘要：

针对北京快速城市化影响下的农村居住用地大量非法流转、亟待规范管理等现状特点,选择海淀区肖家河城中村和通州区张家湾镇小产权房分别作为非正规住房租赁市场和非正规土地交易市场,开展微观案例研究。结果表明：城乡二元土地制度是农村居住用地非正规市场形成与发育的制度根源,城市化快速发展与低价住房供应严重不足为其宏观背景,农民对现行土地征用与补偿制度的日益不满和主动争取分享土地增值收益的强烈意愿是其内在原因。非正规市场采用＂低成本-低地租-高利润＂的微观运作机理,市场参与个体（农民与消费者）可获得较好的经济收益,但也要承担较高的风险;对于城市与社区,非正规市场则会带来较严重的经济社会与资源环境等方面的负面影响。

英文摘要：

Under market reforms and as large Chinese cities are experiencing rapid expansion in the last three decades,rural land in the fringes and suburbs has been transformed into tradable commodity.This process has seen peasants losing their traditional livelihood attached to land and unable to cope with new urban-based jobs.This paper is based on a theoretical exploration of China＇s informal market of rural residential land,supported by a case study of urban villages＇ in Beijing which have experienced rapid urbanization.Our analysis shows that the dualistic rural and urban land systems which have given rise to China＇s urban-rural dichotomy in land rights are institutionally the root cause leading to the formation of the informal market.Peasants deprived of such rights receive little compensations when their lands are expropriated.This paper investigates the response and counter-measures of the Beijing peasants in creating an informal market to generate their own incomes and share of the surplus value＇ resulting from land use conversion.They rent out rooms to low-income earners and undertake informal sales of apartments to Beijing residents.However,the land allocation efficiency in the informal market is inferior and land rent distribution is also inequitable due to imperfect market operations and speculations.The field surveys of Xiaojiahe Urban Village and Taiyuyuan Small Property Housing have characterized this institutional origin,and their operating mechanism is provided in detail.The informal land development has brought wealth to peasants,but incurred low efficiency in land use as well as handicaps in public services provision.It is recommended that,for rural zones situated at the city＇s fringes subjected to pressures of being urbanized,land codes and public policies relating to both the urban state-owned land market and the rural collectively-owned land market integrated and examined as an entity.Policy considerations such as protection of farmland,regulations on land expropriation including rights to