The development of micro-grid renewable energy system in China has achieved rapid growth in recent years, and the micro-grid renewable energy system has been drawing more and more attention by its flexible operation. Due to the randomness, fluctuation, uncertainty of the wind and photovoltaic renewable generation, abundant flexibility is required to meet the needs of safe, reliable and independent operation of the micro-grid energy system. We need to connect large energy systems to accept outside assistance when the micro-grid renewable energy system is short of adjustment capability. Independent operation and network operation will affect the economic benefit of the micro-grid energy system, so it is practically meaningful to study on the economic benefit evaluation of the micro-grid renewable energy system. This paper proposes a micro-grid energy system operation simulation model about wind and photovoltaic generation, the uncertainty of which is tackled based on the scenario generation and extraction techniques. Based on the proposed indices, the economic benefit could be evaluated by simulating the micro-grid energy system operation. The proposed method is validated by a real micro-grid energy system.