The invention relates to an optimal power flow solution method of a power system. The optimal power flow solution method comprises the following steps of 1 building an optimization model correspondingto the power system, wherein the optimization model is constrained by a power balance constraint condition of the power system, a constraint condition of a system decision variable and a probabilityconstraint condition of a system state variable; 2, eliminating the system state variable and the power balance constraint condition which are involved in the optimization model after the system statevariable which is described by employing the system decision variable and a system random variable is obtained by a point allocation method; 3, determining division points corresponding to the probability constraint condition of the system state variable according to Cornish-Fisher expansion so that the probability constraint condition of the system state variable is converted to a certainty constraint condition of the division points; and 4, obtaining the converted certainty optimization model, converting the certainty optimization model to a target function, and solving optimal solution ofthe target function so as to obtain optimal power flow of the power system. By the optimal power flow solution method, the solution efficiency is improved.