Grid-connected microgrids play an important role in improving local electricity economy and the power supply level.Take a typical wind-solar-battery grid-connected microgrid as an example.Taking into account such economic factors as the initial investment cost，the replacement cost，the operation and maintenance cost，salvage，the electricity cost，etc.，and operating power constraints，the optimal sizing schemes of different self-balancing capabilities under the economic objective are discussed from the perspective of user benefits.The genetic algorithm（GA）and mixed integer solver software CPLEX are adopted to obtain the power economy of the grid-connected microgrid of different self-balancing capabilities and the influences on optimal scheme of different electricity selling prices，which can provide a reference to optimal sizing and design of the grid-connected microgrid.