In the global energy crisis and environmental pollution problems, vigorous development of clean energy is a common initiative of all countries in the world. As an important means of new energy consumption and reliability improvement of power supply, micro-grid has a very broad development prospect. In order to overcome the problem of low efficiency of traditional MCS calculation, an micro-grid GSA method based on sparse polynomial chaotic expansion in the paper is proposed, which is used to accurately and quickly identify key input random variables that affect the operating state of the system. Furthermore, the accuracy and efficiency of the proposed method are verified by the example analysis of the island micro-grid.