A new method is proposed to solve the reliability of power system state estimation problem and the execution efficiency problem. In this method, the state estimation result is no longer computed by estimation criterion to obtain the only "optimal" or "suboptimal solution", but contains a result set of several feasible solutions (that is, the power system state). According to the known reliability of the solution, the trusted state set is obtained, and the reliability of power system state estimation is solved. As a result, the computational efficiency is improved and the time of state estimation is reduced effectively. Applying the algorithm to optimal power flow model, the IEEE-118 node test system example shows that the algorithm can ensure the security of the node voltage, has high computational efficiency, moreover, it is cost-efficient.