Abstract: The purpose of this research is to Provide the basis for solving the problems of shortage of urban land use and improving availability of low hill gentle slope land according to analysis the suitability to converting the mild slop of low mountains and hills to construction land in the tree counties and two districts of Baiyin Area with methods of differential regularization method and entropy method. It showed that, Jingtai County and Jingyuan County were highly suitable to convert the mild slop of low mountains and hills to construction land, and Pingchuan District Baiyin district were the medium suitable and Huining County was the lowest. Therefore, we could draw a conclusion that Jingtai County, Jingyuan County, Baiyin District and Pingchuan District had high suitability and comprehensive conditions to convert the mild slop of low mountains and hills to construction land under current circumstances. Huining County was not suitable to the development, but by taking some biological and engineering measures, Huining County could improved in regional conditions to conduct the converting program.