Abstract: The paper synthetically presents the principle and methods of 3D geostress measurement by hydraulic fracturing technique used both in 3 boreholes with 3 different directions and in one borehole. The data procession calculation formula for the two methods were strictly derived to possess strong operability in practical engineering. The methods have been used in the geostress measurment for Shuibuya Project and Xuan′en Dongping Hydroproject, the results have a good agreement with those obtained by 2-D geostress measurement. As the methods have supplied the deficiency of traditional geostress measurement, which can only measure 2D cross-sectional stress of a borehole, its applicable scope is thus widened.