The grid-connected micro-grid with large scale has proposed higher requirements for grid Demand Response (DR). This paper introduces factors of micro-grid into the DR system and designs the structure of micro-grid based DR system, together with the modeling principle and method of micro-grid based DR policy. On this basis, this paper proposes a micro-grid based demand response optimization policy under both conditions of time-of-use price and real-time price. According to the characteristics of micro-grid based DR system, situational evaluation is conducted by taking the DR system in someone area of Shanghai as an example. Simulation results show great efficiency of demand-response optimization policy proposed with both of the time-of-use price and the real-time price. This work is supported by Science and Technology Project of State Grid Corporation of China (No. 52094015001A).