Abstract:The variable step-size affine projection algorithm attracts wide attention for its advantages of simple frame, fast convergence rate and so on. However, the high complexity of this algorithm limits its application. To reduce its complexity，a new method is proposed which changes its step size based on evolving order. According to the condition of convergence on the Mean-Square Deviation, the algorithm decreases its order as iteration goes on. Simulation results show low complexity, fast convergence rate，and low misadjustment of the proposed algorithm.