As we all know, the calculation of network reliability is a typical NP-hard problem. The method of calculating network reliability using pathset matrix and boolean operation is simple and easy to program. however, there exists a serious combinatorial explosion problem with the increasing complexity of a network. And the research of this method is just limited to the achievement more than improving efficiency. This paper starts with the pathset matrix and improves the efficiency form decreasing the memory utilization and redundancy. Some examples are given to prove the efficiency of the improve algorithm. And the efficiency of the improved algorithm is illustrated by examples.