For the situation that the controller's expression in a nonlinear closed loop system is a nonlinear function we constructed a linear affine function of the output data based on the parameter estimation iterative method by using the virtual reference feedback tuning control design principle.Through minimizing the approximation error we could seek the adjustable weights in the linear affine function by using the parameter estimation method of system identification theory.Then we could approximate the former nonlinear controller using a linear affine function which included some adjustable weights.Finally the efficiency and possibility of the proposed strategy was verified by the simulation results.