An algorithm based on mutual information （MI） is proposed for the time resource optimal allocation of phased array radar （PAR）， which focuses on multi-target tracking under active suppression jamming. The MI criterion is used as the quantitative indicator of target tracking， and the MI expression of the radar echo and the path gain matrix which contains the time variable is derived. Then the time resource optimal allocation model is established， and the improved genetic algorithm is used to solve the model. The simulation results show that the algorithm can maximize the number of effectively tracked targets under active suppression jamming， and the overall tracking performance of the effective tracking targets is improved.