The correlation between K’( the amplification effect coefficient of blasting vibration) and ratio R/S( R is the distance to blasting center,and S is the length of horizontal projection of the distance R) was analyzed based on the large amounts of test data of blasting vibration obtained from some tunnel project. It is found that the K’value was positively associated with the ratio R/ S. When the ratio R/S varied from 1 to 5,the K’value increased quickly; When the ratio R/S was more than 5,the K’value increased slowly,finally leveled off; the K’value could not increase unrestrainedly with the with the increasing of the ratio R/S. The law of amplification effect of blasting vibration has been verified by actual tested results. The result of the study has some practical significance to the forecast of vibration effect and the theoretical study on amplification effect of vibration for blasting project under complicated condition of city.