The most common approach of researching the hydraulic characteristics of the diversion tunnel is model test, which exists some shortcomings such as scale effect. The universal software Fluent is applied to study the hydraulic characteristics of diversion tunnel. The distribution of pressure along the flow direction, velocity, the flow condition and so on is calculated. Compared with computation results and the model test results of several typical sections, the results are in good agreement with model test, which verify the feasibility of numerical calculation method. The numerical calculation method can be used as the auxiliary methods of model test and provides the reference for Fluent software in the shape optimization design of the diversion tunnel.