Abstract: This kind of soil is formed during the chemical weathering of carbonate rocks.It exhibits high water content and high plasticity. When structures are constructed on red day foundations, the soil often needs to be treated due to its soft properties, Although the method of mixing of rail and cement is commonly used to improve soft soil, intensive studies on its affect are relatively few. Unconfined compression tests are performed on the cemented red clay. The basic mechanics parameters of this kind cement soil can he got by experiment. After the regression analysis of the experimental result,it can he given that influence factors for cement soil strength and relation between it,and the strength calculate formulas of different cement contents and cure ages.