Abstract: This paper studies an iterative method of estimating parameters in Gamma distribution based on maximum likelihood estimation and EM algorithm improved by non gradient information spectrum residual method in the case of classified data, Type-I interval censered data, Type-II interval censered data, and it proves the strong consistency of the algorithm. The simulation results show that the iterative method proposed in this paper can greatly shorten the running time while ensuring the accuracy, the estimated mean square error tends to zero with the increase of sample size.