Abstract A volute-type mixed flow pump is taken as an example to construct a leak-free model based on pressure distribution theory. A leakage model based on the true flow of the pump cavity was proposed and constructed. The flow of the two models under the conditions of 0.03Qopt-1.20Qopt was simulated. The curves of the respective axial forces with the flow rate were calculated, and the numerical calculation results, theoretical calculation results and experimental results were compared. Meanwhile, the accuracy of different calculation methods and the influence of leakage flow on axial forces were analyzed in detail. The results show that the back cavity pressure of the impeller cover is the main factor for the generation of axial force, and the leakage flow can effectively reduce its internal pressure; the numerical calculation method based on the leak-free model and the theoretical calculation method are both based on the assumption that there is no leakage in the chamber of the cover, ignoring the influence of leakage flow on axial force, lea-ding to a large deviation between the calculation value and the test value. The maximum errors of the two calculation methods are 25% and 44% respectively; the numerical calculation data of axial force based on the leakage model are close to the test data, and the maximum error is within 10%. The calculation accuracy has been greatly improved, indicating that the numerical calculation method of axial force based on the leakage model has higher accuracy and feasibility.