Abstract: The quantification of system strength in power systems with high-penetration renewable energies based on known model parameters has relatively clear methods and conclusions. There is still a need for strength evaluation methods based on the local measurement information. A real-time measurement method of the system strength is established in this paper. First, the real-time short circuit ratio(RSCR) and its critical index(CRSCR) are constructed, and the safety margin can be analyzed by comparing them. Furthermore, the corresponding RSCR margin is calculated based on the active power margin constraint and the low voltage constraint, respectively, and the functional relationship between RSCR, power, and voltage analyzes the index adaptability under different types of safety constraints. Then, the system architecture and the real-time measurement algorithm process covering the Thevenin equivalent parameter real-time estimation, the indexes calculation, and the safety warning are built. Finally, simulations validate the accuracy of the RSCR and CRSCR and the effectiveness of the real-time measurement method. The real-time measurement method based on local information supports higher penetration of renewable energies connected to the grid.