Abstract: As the scale of renewable energy integration in the power system continues to increase, the scenario of renewable energy stations connected to weak AC grid appears in some local areas, giving rise to broad-band oscillation or overvoltage, which restricts the security and stability operation of power system. Aiming at determining the scale of renewable energy integration, it is of great urgence to propose a quantitative index which possess solid theoretically foundation as well as practical engineering background. In this regard, firstly, based on the physical meaning of short circuit ratio, considering mutual influence of multiple renewable energy stations, the definition and calculation method of multiple renewable energy stations short circuit ratio (MRSCR) was proposed. Calculation formulas for different application scenarios were derived according to the correlation between system impedance ratio and short circuit ratio. In what follows, a qualitative analysis of the critical index of MRSCR was carried out, and the critical MRSCR index was proposed through calculation with practical power system parameters. Finally, the MRSCR calculation module was developed based on PSASP, and time-domain simulation was carried out, which verified the effectiveness of the proposed MRSCR and its critical index for the indication of the power system voltage strength.