Considering the operation constraints of main equipments, this paper addresses an optimization design and coordinated operation control strategy for an islanded microgrid including wind generator, photovoltaic, diesel generator and energy storage (Wind-PV-DG-ESS). The primary design objectives of this strategy are: (i) to guarantee the long-term operation stability of the islanded microgrid; (ii) prolong the service life of energy storage batteries; (iii)and make full use of the renewable energy. It also includes an optimization design method aiming to minimize the net present cost (NPC) associated with the full life cycle. A traversal algorithm based on renewable resources penetration is implemented for optimal sizing of distributed power supply and the capacity of energy storage system for testing system. The microgrid optimization design tool named QSOT-MG developed independently is employed to verify the effectiveness of the proposed control strategy and optimization design method through simulation results comparison with the diesel-based only system. The different penetrations impact of renewable energy on NPC, fuel consumption and capacity of system components are investigated, which shows that proposed method can result in significant cost saving and fuel consumption decreasing because of the availability of system components in the case of high penetration.