Abstract: The return angle stiffness of tilting mechanism can be taken to judge the return safety of tilting trains is put forward. Return angle stiffness describes the stability of car-body returning to neutral position when tilting mechanism loses power during the car-body tilting. When the return angle stiffness is positive, the car-body can return to the neutral position under the action ofweight. When the return angle stiffness is negative, the car-body can not return to the neutral position. When the return angle stiffness is zero, the car-body is in a critical position. Therefore, the return angle stiffness can be used as a criterion for evaluating the return safety of tilting trains.