Abstract: In this paper,the mechanics analysis for the traditional 3-D hydraulic fracturing in-situ stress measurment method is done,and a new theoretical model proposed.The minimum principal stress criteria adopted in the new model,compared with the minimum tangential stress criteria of traditional method,illustrates the mechanism during hydraulic fracturing procedure more objectively.To illustrate the procedure of this method and its applicability,the genetic algorithms inversion technique is adopted to estimate assumed stress state.The results show that the method is applicable.