The involute external meshing gear pump is widely utilized in various fields such as mining and engineering due to its simplicity structure and low cost.However,there is a scarcity of literature on accurate calculations of instantaneous flow and displacement.To address this,a mathematical and simulation model of the instantaneous output flow of the gear pump was established,based on the gear meshing mechanism,tooth profile,and the angular position relationship of meshing points.The impacts of contact ratio,modification coefficient,unloading groove,side gap,and other factors were demonstrated by the model.Additionally,a precise method for calculating the displacement of involute external meshing gear pumps was proposed,and the instantaneous flow of different types of pump were simulated with Simulink.And three different type of gear pump were used to verify the displacement formula.The maximum error is within 5%.After validating the effectiveness of the calculation model,a gear pump calculation auxiliary platform was developed.The performance visualization of the instantaneous flow and displacement of the external meshing gear pump was realized,to simplify the calculation process and be more well-suited for engineering applications.