Abstract: To solve the shortcomings of traditional PID controllers in dealing with disturbance rejection and robustness,and the over-reliance of model-based control algorithms on mathematical model of the controlled system,a model-free adaptive control algorithm is proposed for discrete time MIMO(multiple-input multiple-output) nonlinear systems.In this algorithm nonlinear system is linearized by linearization of partial format.Then the controlled system parameters are identified on-line by a novel projection algorithm.The parameters are used to recursively compute model-free adaptive control rule.The controller is designed only by using I/O data of the controlled system,and no structural information or external testing signals are needed.So the impact of the unmodelled dynamic problem of the modeling process on system performance doesn't exist.Simulation result shows that the proposed algorithm is an effective strategy with excellent tracking ability and strong robustness.