Abstract: Based on many seismic records of loess area in northwestern China during Wenchuan earthquake,a direct fitting method is used to obtain the soil site acceleration peak attenuation relationship of the loess area in northwestern China.The soil site acceleration amplification formula in loess area of western America is obtained on the basis of the relevant research results.With the revision method proposed in the paper,soil site acceleration amplification formula in loess area of western America is amend,and then the similar formula in loess area of northwestern Chin is obtained.Furthermore,the bedrock site acceleration peak attenuation relationship in loess area of northwestern China can be obtained although lacking of bedrock acceleration records.