Abstract: When oil is produced with screw pump, the rotary speed directly affects the pump’s efficiency and service life- The demands to the pump’s characteristic is different at different occasion, working condition servicing stage and when different pump is adopted, therefore, the rotary speed should have different selection. If the selection is not reasonable,the high efficiency and energy saving advantage of screw pump can not bring into play. Analysis and discussion were made to the important factors affecting the rotary speed selection of the screw pump from two aspects of theory and actual application, which possessed a certain reference value to the design and application of the screw pump.