Aimed at the optimal configuration problem of standalone microgrid, the uncertainties of wind power, photovoltaic (PV) power, and load are modeled using their probability model and sequential Monte Carlo simulation. A multi-objective optimal model considering the net present cost in the full life cycle and the carbon dioxide emissions in every year is proposed. In this model, the probability constrained concerning the reliability is appended, and the non-dominated sorting genetic algorithm-II is used to solve the multi-objective model. Examples analyze the effects of different confidence level of reliability and diesel price on the optimal results, which prove the validity of proposed model and algorithm.