Abstract: In order to study the transport performance of the circular oscillating internal gear pump for aviation under the condition of mixed transport of oil and gas, this paper took the volume efficiency as the performance index of the gear pump, and by using the Reynolds time mean k-ε turbulence model and the VOF two-phase flow model based on Pumplinx to simulate. The effects of different running speed, end clearance, rotor stage and rotor thickness on the volume efficiency of gear pump under the condition of oil and gas two-phase were analyzed. The results show that when the oil content of the inlet section is low, the volume efficiency of the gear pump first increases and then decreases with the increase of the rotational speed. When the oil content is 70%, the maximum reduction of volume efficiency is 27.79%; when the gas content of the inlet is high, the volume efficiency decreases with the increase of the rotational speed; the volume efficiency of the gear pump decreases with the increase of the end clearance at different inlet sections. When the oil content of the inlet section is low, the volume efficiency of the gear pump is negatively correlated with the increase of the rotor series; when the oil content of the inlet section is high, the volume efficiency of the gear pump is positively correlated with the increase of the rotor series; the volume efficiency of gear pump decreases with the increase of rotor thickness under different inlet sections, and the maximum value of decrease is 35.51%.