Harmonizing the contradiction between economic growth and cultivated land conservation has important effect on the realization of sustainable development in China,and rural-urban land conversion is the focus of that contradiction. Rural-urban land conversion patterns are governed by a broad variety of potential driving forces and constraint which act over a large scale. It has been recognized that the types and effects of rural-urban land conversion drivers may vary with spatial scale and multi-scale investigation of rural-urban land conversation patterns which is essential for fully understanding of its complexity. From the viewpoint of social and economic factors that influence rural-urban land conversion,this paper analyses the driving mechanism for rural-urban land conversations in different spatial-temporal scales by using province data from 1999 to 2004. The results show that: (1)Relationships obtained at a certain scale of analysis may not be directly applied at other scales and the variables included in the models and their relative importance varied between rural-urban land conversion types. (2)Temporal scale effect in driving mechanism of rural-urban land conversion in China changes as follows: as long as the time influences forces for rural-land conversion,but different factors have different driving effects passes by,GDP,fixed assets investment and population increase which always used to be the main factors affect conversion. In 1999 and 2004,one percent increase in fixed assets investment will make 0.1548ha and 0.4344 ha rural land be converted into urban land,one percent increase in GDP will make 0.1969 ha and 0.2968 ha rural land be converted into urban land,one percent increase in total population will make 0.4469 ha and 0.0351 ha rural land be converted into urban land. (3)Spatial scale effect in driving mechanism of rural-urban land conversion in China changes as follows: One percent increase in GDP and fixed assets investment will make 0.20372 ha and 0.4909 ha rural land be converted into urban land,which obviously influence rural-urban land conversion in the eastern provinces; one percent increase in industrial structure upgrade and fixed assets investment will make 0.23089 ha rural land not to be converted into urban land and 0.1151 ha rural land be converted into urban land,which show the most obvious influence on rural-urban land conversion in the middle provinces; one percent increase in GDP and total population will make 0.2008 ha and 0.24901 ha rural land be converted into urban land,which obviously influence rural-urban land conversion in the western provinces. Some valuable propositions are presented.