On the basis of summarizing the existing methods of main connection reliability analysis, this paper puts forward a minimal cut-set method based on adjacency matrix. For any kind of main connection, we can get the minimal path matrix and the fault response matrix as long as the adjacency matrix of elements is given. Then we can analyze the failure of the system caused by component fault clearance. The element substitution matrix and the affected matrix of elements can also be obtained by adjacency matrix and we can analyze the running status of power system after switching operation. This method avoids complicating the element models and it is more in line with the actual operation characteristics of the power system. The most important thing is that this method is easy to program. In this paper, the reliability analysis of several common main connection is carried out by using the above method, and the practicability of the method is proved.