The wheel-rail contact force is the key factor for the railway vehicle running safety. This study aims to find the vehicle-based method for measuring wheel-rail contact force on-board. The method is based on the dynamic force equilibrium of wheelset. The vertical and lateral contact force is able to be determined while some sensors are used to measure the dynamic responses of bogie for some necessary information. In order to verify the correctness of the method, a 1:5 scaled bogie with rolling rig is developed to perform the experiment. Laser displacement meters are used to measure the compression of the suspension spring for determining suspension force. And acceleration meters are used to determine the dynamic inertia force while the wheelset is moving. Then the vertical (P force) and lateral (Q force) wheel-rail contact force can be solved through the equations of equilibrium. Finally, the derailment coefficient can be calculated by P and Q force to evaluate the running safety of the railway vehicle under different running speed. A convenient method with cheap devices are proved to be able to measuring the real time wheel-rail contact force on board. Hope that this method can be used to prevent the disaster (such like earthquakes) to the railway vehicle in the near future.