According to the principle of Wankel engine transmission, a double inlet and outlet triangular rotor pump was designed, and the working principle, structural characteristics and mathematical model of cylinder line of the triangular rotor pump were described. Mathematical model of mechanical losses of the new pump such as seals loss, rotor end loss, bearings loss and gear meshing loss was built. The working fluid in the pump was numerically simulated by using Fluent. The results of numerical simulation and mathematical model were used to calculate and analyze the flow rate, pressure, mechanical loss and mechanical efficiency of the triangular rotor pump, and the results of numerical simulation were verified by experiments. The results showed that at a rated speed of 190r/min, the inlet flow rate was fluctuated, and the three working chambers alternately performed suction and discharge, and the total outlet flow was relatively stable. The pressure cycle of one work cycle of the working chamber included four phases of the working chamber expansion phase, the rapid pressurization phase, the stable output phase, and the rapid depressurization phase. The flow rate and pressure recorded in the experiment agreed well with the predicted values. With the increase of the rotational speed, the pressure and flow rate were significantly 〖JP3〗increased. The predicted values of the flow rate and pressure at the rated rotational speed were 8.96m3/h and 2013.92kPa, respectively. The friction loss of the seals, rotor end, bearings, and gear meshing at the rated rotational speed obtained by the mathematical model of mechanical loss were 103.4W, 182.5W, 60.5W and 33.2W, respectively, and the predicted and experimental values of mechanical efficiency were in good agreement, which were 92.9% and 93.3%, respectively.