The invention provides a day-ahead economic dispatch method for a virtual power plant. The method includes the following steps that first, a day-ahead economic dispatch mixed integer linear programming mathematical model making benefits of the virtual power plant maximum is built, and in an objective function, a stochastic programming method is adopted for handling the uncertainty of electricity price; second, constraint conditions are built to make an electric power system meet power constraint, unit operation constraint and contract electric quantity constraint, and in the constraint conditions, a robust optimization method is adopted for handling the uncertainty of generated output of renewable energy; third, a prediction error coefficient and a robust coefficient are set; fourth, calculation software is used for obtaining an optimum day-ahead economic dispatch result. Compared with the prior part, the method has the advantages of being good in calculation result, high in calculation efficiency and the like.