Abstract: Cement-soil mixing method is commonly used in strengthening soft soil foundation.The increase of cement-soil strength with age has a direct influence on the cement-soil reinforcement design,construction schedule arrangement and control,etc.Based on the characteristics of the silt soil of China′s southeast coast,the mechanical properties of cement-soil are studied using five common cements and their strain-stress curves at the age of 90 days are obtained through the lab mixing proportion tests and loading tests.The tests results show that the mechanical properties of cement-soil change with age and kinds of cement.The compressive strength-age formula of the cement-soil is achieved,which can be used to predict cement-soil strength according to 3 days′ strength accurately.It is helpful to improve the construction quality control.