This paper introduces an homotopy algorithm which has convergence stability to solve the alternating current optimal power flow problem. The complicated Alternating Current Power Flow (ACPF) can simplify as simple Direct Current Power Flow (DCPF). The homotopy participation factor is introduced into the linear DCPF to make DCPF convert back into ACPF gradually to realize Alternating Current Power Flow Homotopy method (ACPFH). The homotopy curves are generated to solve a series of nonlinear problems.The traditional method can not solve the unstable points,because the calculate process always turn up Jacobian matrix.But the Homotopy method can calculate all results. It is a superiority for Homotopy,and then can explore power system problem more entirety.This novel algorithm is different from Newton - Raphson method, because it isnt sensitive to the initial point selection and has the global convergence.The homotopy algorithm is applied to IEEE - 3, 9, 14, 30, 36, 57, 118 node testing systems for power flow optional calculation, the simulation results show that the novel algorithm can solve power flow problem better and its calculating speed is much faster than the traditional algorithm, it can calculate the optimal value more direct.