In order to solve the difficult machining problem of the inner spiral surface of double equal wall thickness stator of positive displacement motor in shale gas development,the numerical simulation model of the external high-pressure forming of the double equal wall thickness stator was established.The influence rules of the geometric size of the tube blank,the hydraulic pressure magnitude and springback on the forming quality of the stator were studied.The accuracy of the numerical simulation model was verified by experiments and 3D measurement.The results show that the tube blank geometry size is proportional to wall thickness,equivalent plastic strain,displacement,residual stress and clearance value.The forming hydraulic pressure of 150 MPa or above has almost no effect on the equivalent plastic strain and wall thickness.The springback of stator bulging area is greater than that of transition area and contact area.When the forming hydraulic pressure is 210 MPa and the inner diameter of the tube blank is 88 mm,the forming quality of the stator is the best.