Abstract: A new type unsymmetric gear pump with double pressure angles was studied.New formulas for the instantaneous flow and flow pulsation were put out.Compared with symmetric gear pump,the formulas showed that the unsymmetric gear pump could efficiently improve flow pulsation with the rise of instantaneous flow.It is concluded that the sliding coefficient of unsymmetric gear pump was smaller than that of symmetric gear pump.The increase of pressure angle of work side would cause an evident increase in the minimum oil-film thickness and in the specific ratio of oil-film thickness,which is helpful to improve the lubricant characteristics of gear teeth surface.The practical significance of the present gear is demonstrated by the computer simulation with MATLAB software,such predictions can provides the firm basis for the further engineering application of this new-type gear pump with unsymmetric teeth and double pressure angles.