Introducing large-scale plug-in electric vehicle into a power system would produce extensive impacts on power system planning, operation as well as electricity market development. Hence,it appears necessary to properly control the PEV charging and discharging behaviors. A mathematic model of economic dispatch considering PHEV（Plug-in Hybrid Electric Vehicles）is built，which takes the minimum unit coal cost as its objective function and establishes corresponding constraints.A crisscross optimization algorithm (CSO) with dynamic constraints handling is proposed to solve the model and obtain the optimal dispatch scheme. The CSO algorithm adopts a double cross mechanisms, which are horizon cross and vertical cross, whose combining enhances the global convergent ability while the introduction of competitive mechanism drives the potential solutions approximate the global optima in an accelerating fashion without sacrificing the convergence speed. A 10-unit 24-hour Unit Commitment problem is employed to demonstrate the feasibility and efficiency of the developed model.