The volume efficiency of the high-power external gear pump is insufficient at high speeds, rendering it inadequate for meeting the demands of high-speed electric construction machinery. Firstly, the 3D model of the traditional pump was established, and the mathematical model of the oil suction flow-pressure of the tooth cavity was derived based on the obtained structural parameters. Furthermore, an optimization scheme of oil suction runner based on “π” groove design was proposed to improve the volume efficiency by analyzing the mathematical model of oil suction flowpressure in the tooth cavity. Then the structural parameters of the full factor orthogonal design were simulated by using Pumplinx, and a prediction model for optimizing pump volume efficiency was established. Finally, the performance of the optimized pump was verified by experiments. The results showed that when the radial oil suction was small, the instantaneous pressure required by the tooth cavity to fill the oil was large, and the filling time of the tooth cavity was shortened when the pump was running at high speed, which was the main reason for the decrease of the volume efficiency of the pump at high speed. Through the combined radial and axial oil suction method, the minimum volume ratio required for radial oil suction (Δp≥0.1MPa) was reduced by 42.62 percentage points at 3000r/min, resulting in a high liquid filling rate of the tooth cavity. The influence degree of the optimized structural parameters on the volume efficiency was d2, Rm, d1 in order from large to small, and the prediction model for volume efficiency, with an R2 value of 0.9971, demonstrating high reliability. The volume efficiency of the traditional pump was decreased rapidly when the operating speed exceeded 2700r/min, and dropped to 81.87% at 3000r/min. However, the optimized pump exhibited a gradual decline in volume efficiency beyond 2700r/min. However, the volume efficiency of the optimized pump experienced a slow decrease. In comparison with traditional pump, there was an increase in volume efficiency by 1.8 percentage points, 6.79 percentage points, and 11.64 percentage points, respectively at speeds of 2800r/min, 2900r/min, and 3000r/min.