The mechanical properties of supersulfated cement (SSC) and Portland cement under hydrochloric acid attack were investigated, and the deterioration mechanism by acid erosion was discussed in this paper. The compressive strength of SSC paste in hydrochloric acid and water were measured and the compressive strength retention rate was calculated. The changes of the types and quantities of hydration products and the evolution of microstructure were analyzed by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TG-DTG). The experiment results show that the main hydration products of SSC are ettringite and calcium silicate hydrate, which are different from Portland cement. Compared with Portland cement, SSC shows better compressive strength retention rate and resistance to acid. The deterioration of SSC in hydrochloric acid can be attributed to the dissolution of main hydration products. There are dihydrate gypsum and a lot of silica gel in SSC system, and silica gel in Portland cement after erosion.