Abstract: The vibration state of bridge is a key index in evaluating whether the structural dynamic design parameters are reasonable. Beams with variable cross-sections may provide a better or more suitable distribution of mass and strength and therefore can meet special functional requirements in architecture, robotics, aeronautics and other innovative engineering applications. Dynamic responses of beams with constant height and variable cross-sections under moving vehicles are studied. It has both theoretical significances and practical application values. The control equation of the simple beam under moving forces is established, and the comparatively precise theoretical solution is obtained. Then the numerical verifications of both finite difference method and ANSYS finite element method are given. They all receive a good result. Finally, the impacts caused by the changes of non-uniform factor and vehicle speed are discussed.