Abstract: Because there was dissension in the maximum principal stress orientation obtained by in-situ stress measurements by different results measurements,the principal stress axis was determined by conjugate joints,fault occurrence,rake angle and shift symbol of fault slip.Plumose fracture and orientation of dislocation was applied to find out whether sharp angle zone or obtuse angle zone between two groups of conjugate joints was compressive zone.The method was applied in Dahuofang reservoir conveying-water engineering and the results indicated that the orientation of the maximum principal stress was nearly EW and identical with the measured data except the measuring points 6,7,8 and 12.The present method could be used to verify whether the measured data was exact or not.