The key of vector control system is whether the flux linkage can be accurately positioned. Taking the advantages and disadvantages of traditional voltage- and current-model flux observers and their application scope into consideration, a voltage and current combined flux observer is proposed. Smooth switching between voltage and current models is achieved through proportional integral control. The trapezoidal method is used to discretize the combined flux model, which realizes the digitization of the vector control system of induction motor. The physical experiment platform based on DSP28055 is built. The experimental results show the effectiveness of the method and the feasibility and superiority of the combined flux model in induction motor vector control system.