The present disclosure provides a system-level protection system and method for sub/super-synchronous resonance/oscillation. The system includes a centralized protection coordinator arranged in a control center and a plurality of distributed protection relays arranged in a plurality of transformer substations or wind farms. Each distributed protection relay is configured to acquire a sub/super-synchronous impedance of the wind farm. The centralized protection coordinator is configured to acquire the sub/super-synchronous impedances measured by the plurality of distributed protection relays, to obtain a sub/super-synchronous aggregate impedance of the system according to a preset circuit topology and the sub/super-synchronous impedances, and to generate a system-level protection signal when the sub/super-synchronous aggregate impedance does not meet a stable condition. Each distributed protection relay is further configured to initiate a system-level protection according to the system-level protection signal.