The invention relates to equipment for dynamically detecting parameters of railway vehicles, in particular to a system for dynamically detecting stiffness parameters of closed-loop diagonal-bracing type vehicle bogies. The system consists of a mechanical system, a testing system and a control system, wherein the mechanical system comprises a body vertical thrust block assembly (II), a dynamic detection table (III) for the stiffness parameters of the closed-loop diagonal-bracing type vehicle bogies, and a hoisting-type upper beam pillar (V); the dynamic detection table (III) for the stiffness parameters of the closed-loop diagonal-bracing type vehicle bogies mainly comprises a closed-loop diagonal-bracing type vertical loading gantry (A), a plane loading platform (B), an adjustable-gauge bridge approach device (C), a bogie longitudinal anti-thrust assembly (D) and a simulation corbel (F); the testing system comprises a displacement detection system (G) and a six-dimensional force sensor (c); and the control system mainly comprises a hydraulic control system, an electrical control system and a computer system. The system can perform dynamic test on the stiffness parameters of the bogies in an entire-vehicle state and an independent state.