摘要： 软件可靠性越来越受到重视，倒是早期的模型能提供实际情况很好的近似，仍受到重视。本文对软件可靠性的著名模型-JM模型进行了修改并进行了研究，给出了模型中的参数的极大似然估计存在的充要条件

Abstract: The software reliability is more and more given attention to. The models given before are given attention to now because they are accurate to the truth. In this paper, we modify the famous Jelinski-Moranda model, and give a necessary and sufficient condition for existence of the maximum likelihood estimators of the parameters of the new model .