To study effect of limestone powder on the properties of magnesium phosphate cement(MPC） paste, the initial setting time, compressive strength, shrinkage deformation and hydration temperature of MPC paste with limestone powder added were investigated, the phase composition and micro morphology of MPC paste with limestone powder added were analyzed. The results show that some limestone powder added significantly improves the compressive strength and shrinkage deformation of MPC paste. Some limestone powder added remarkably improves early hydration degree of MPC paste, and increases the crystal degree, formation amount and ratio of main hydration MgKPO4·6H2O, and change the shape and size of crystal MgKPO4·6H2O, resulting in the more compact structure of hardened MPC paste.