In this paper the effects of ZnCl_2 and ZnSO_4 on setting time, heat of hydration, resistivity and compressive strength of cement were studied. Results show that with increasing amount of ZnCl_2, the hydration exothermic rate is lowered, hydration and hardening of cement is delayed, the resistivity development and the early strength are reduced, effect on 28 d compressive strength is slight. Moreover, with respect to ZnSO_4, when use level is 0.10%, cement final set was accelarated by 50 min. When use level is more than 0.10%, the hydration exothermic rate was lowered. And the resistivity is developed slowly. The cement hydration process is delayed. But strengths are not influenced. The retarding effect of ZnCl_2 is larger than that of ZnSO_4 with the same use level. The effect of zinc salts on cement hydration process not only has something to do with the mass of Zn~(2+), but also with their negative ion.