For calculating stiffness of rail vehicles tumbler locating structure, primary suspension vertical, horizontal and longitudinal dynamic model of tumbler locating were built, composed stiffness calculating formula of which was derived through balanceable force and moment, geometric distortion and conversion of energy and examined by test. The results showed that test results of primary vertical and longitudinal stiffness was consistent with design, yet test result of horizontal stiffness had greater error; furthermore, a better test method was put forward to improve testing precision.