An experimental study of an active body-weight support (BWS) system for improving treadmill-based locomotion training is performed. The dynamical foundation of the proposed system is developed based on a simplified cable suspended mass-spring-damping system which is used to mimic the vertical gait of a walking human. A specifically designed cable pulley suspended cam-slider system is used to mimic the walking gait of a human in vertical direction. A load cell is installed to connect the slider and the cable which is driven by a winch based on the acceleration feedback. The contact force between the slider and the cam is measured to evaluate the walking load of the system. The experimental results demonstrate that the proposed active BWS system can simultaneously reduce both gravitational and inertial load of the walking body, which implies that the walking body suspended in such a BWS system will dynamically behave as if certain amount of body mass had been removed.