Abstract: The incorporation of fly ash into cement-soil can improve its performance in a certain extent. The deformation characteristic is an important index of actual engineering applications. Therefore, researching the effects of fly ash and ages on deformation characteristics of cemente-soil has a great reference value to actual engineering applications. The unconfined compressive strength test of 0 and 8%fly ash cement-soil is done. The experiments show that the growth of the curing age and the addition of fly ash are beneficial to the growth of cement-soil deformation modulus. Especially, the addition of fly ash is beneficial to the growth of the late deformation modulus. By further analyzing the unconfined compressive strength and the average deformation modulus of 0 and 8% fly ash cement-soil specimen, it is found that there is a basically linear relationship between them. Then the conversion formula is derived between them by fitting. Finally, considering the characteristics of stress-strain curve model and regression analysis on the test data, the expression of stress-strain of cement-soil on ascent stage is deduced under the definite condition. The results provide the reference for actual engineering designs.