The study for dealing with the load model in composite system reliability evaluation is almost at a standstill because of the inherent computational complexity. In this paper, an algorithm for composite system reliability evaluation considering load model is proposed. This method is powerful in computation because it can avoid unnecessary state enumeration by means of the relationship among basic reliability informations of load levels. As an example, the IEEE 24-node Reliability Test System is tested on VAX-11/750 computer. The average CPU time to calculate the reliability indices of the system corresponding to a load level is about 5 seconds.