The experimental study on the failure behavior of cement test block in sodium sulfate solution and strength change of specimen in early stage. The microstructure of cement test block attacked by sodium sulfate is observed by means of scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS)and X-ray diffraction(XRD). The mechanism of erosion damage in the sodium sulfate solution is analyzed. It is found that in the early period corrosion intensity will not suffer, but increase, and on the surface no obvious changes can be seen. However, in the attack later coarse surface cracks appear, then there is a serious off and the cement test block eventually collapses.