Abstract: In this paper the responses of 51 sites excited by the Tangshan earthquake are calculated With the down hole measured data, these 51 sites are located in or out of the area of low intensity in Yutian county and the area of high intensity in Ninghe county. Then the relationship of the site index with the seismic shock Parameters (maximum ground acceleration and characteristic period of response spetra) is researched, thus the efficiency of the site index for showing site effect in earthquake is tested.