The prefabricated construction has rapidly transformed the building industry, and achieveing the swift demolding of component is fundamental for the rapid development of prefabricated industry. The effects of sulphoaluminate cement (CSA) at low replacement rate (from 2.5% to 7.5% of cement mass) on the early hydration and mechanical properties of Portland cement were studied. Setting time, compressive strength, hydration heat, XRD, TG, and SEM were used to expose to the behind mechanism, providing solutions for the rapid demolding of prefabricated component. The result show that the incorporation of CSA can shorten the setting time of Portland cement, enhance early hydration, and improve early mechanical properties. With the increase of the CSA mass fraction from 2.5% to 7.5%, the initial setting time reduces by 30%, 43% and 49% respectively, and the final setting time by 24%, 40% and 46%, respectively. 5% mass fraction of CSA increases the 12 h compressive strength from 5.2 MPa to 12.8 MPa, an increase of 169%. Additionally, CSA also improves the later-stage mechanical properties of the system.