This paper is dedicated to analyze the economic issues related to the operation of microgrid system as well as exploring its benefits in improving reliability, energy saving and consumption reduction, environmental protection, investment deferral in transmission and distribution grids from the social perspective. It analyzes its cost and benefits in typical situations by the 2 typical cases of grid-connected and off-grid microgrids compared with that of distributed generator directly connected to power grid. And the key factors affecting the economy of microgrid is discussed.