Compressive strength,impermeability and chloride ion diffusion coefficient of sulphoaluminate cement concrete and Portland cement concrete were tested.The hydration process and the impermeability mechanism of sulphoaluminate cement were studied by means of SEM,mercury intrusion porosimetry.The results show that sulphoaluminate cement concrete have better properties than Portland cement concrete, higher compressive strength,better impermeability,lower diffusion coefficient,because of lower porosity and better distribution of pore diameter.