The present invention relates to a steady-state data-based SCADA telemetry wrong data on-line detection system. The system is technically characterized by comprising a data processing module, a topology data module, a node balance checking module, a line balance checking module, an evaluated value calculation module and an online alarm module. According to the technical scheme of the invention, an effective and feasible method is provided for the online accurate detection of telemetry wrong data. The system can be applied to a scheduling master station. The system serves as one part of a D5000 system and realizes the online and real-time detection function for telemetry data through the node balance and the line balance check based on steady-state telemetry data. Based on the system, the wrong data of telemetry data and a bad measuring point can be timely and accurately detected in the online manner, and then an alarm prompt is sent out. Therefore, reliable telemetry data are provided for the calculation of power grid tidal current, short circuit and stability. Meanwhile, the calculation accuracy for subsequent advanced applications is improved.