The advantages and disadvantages of three realization ways of stability control strategies are analyzed. The development and application demand about the online real-time stability control system in small scale grid is proposed. Firstly, the implementation including hardware structure, software structure and main technical specification of the online real-time stability control system based on ultra real-time simulation is introduced. Then the main technical problems involved in the system are elaborated, including the ultra real-time simulation algorithm, stability control decision, high speed real-time communication program and coordinate scheme with multi-decision ways. The engineering practicability is verified by the application of the online real-time stability control system in independent local power grid and enterprise owned power grid. Finally, the research direction of popularizing the online real-time stability control system in large power grid is expected. This work is supported by Science and Technology Project of Jiangsu Province (No.BZ2015010).