Abstract: PDM（Positive displacement motor） is suitable for drilling directional wells because of its advantages，But it still could not be used for deep wells，highdensity mud wells and smallcurvature wells widely.The PDM′s conventional bushing is a screw surface，it is a variablethickness elastomer stator.It has poor capability to withstand the high mud pressure and a soft mechanism characteristic，is easy to leak，wear and tear，and expand unevenly，its efficiency descends continually.Therefore，the short，highpower，highpressuredrop and lowrotatespeed PDM are developed and applied to improve the drilling efficiency and save cost.In this paper，the mechanics experiment of NBR is carried out，the FEA models of uniform wall thickness and the conventional one are established for calculating.The results indicates，under the same mud pressure when compared with the conventional one，the uniform wall thickness is of less deformation，with the same interference，it has a better seal capability.The equidistant PDM can gain the same torque with less length than the he conventional one.

Key words: drilling, PDM, elastomer, finite element 