In the existence of unpredictable disturbance and large changes in dynamic characteristics,a complete datadriven method based on subspace identification with variable forgetting factor is proposed for LTV multivariable system,without any priori structural information and identification of system parameters matrix.Predictive control is a modelbased control method.In order to establish better system model,the variable forgetting factor is structured by error of the real and predictive output value based on on-line identification.Thus the weight of the collection data is adjusted and identification sensitivity and control effect is improved.Finally,a simulation example is given to demonstrate the efficiency of the proposed algorithm.