Abstract: Geo-stresses,important influencing factors of the stability of the surrounding rock mass,are the natural stress deposited in the rock strata of the earth’s crust.The damping least square method is programmed with the FISH language of FLAC3D which is one of numerical computation software to combine the numerical computation with the fitting computation and the automatism of the fitting analysis is realized.By use of the fitting method,the measured results of the hydraulic fracturing test in the bore #Zk17 of Huangdao water sealed underground oil tank are fitted using the computed results to get the distribution of the geo-stresses in the tank site.According to the fitting results,the major principal stress is 10¹2 MPa,the intermediate principal stress is 6⁸ MPa,and the minor principal stress is controlled by the weight of the rock mass.The tank site belongs to the low-middle geo-stress zone.