Abstract: The vibration characteristics of the space truss girder has been less studied. The continuous Timoshenko beam model is adopted to simulate the space truss girder and the equivalent bending stiffness and equivalent shear stiffness are obtained. The nature vibration of the space truss beam is analyzed based on the energy variational method, and the analytical solutions of vertical vibration frequency and the vibration mode of the space truss beam can be derived. Then the finite element software ANSYS is adopted to simulate different cases, and the frequency and the vibration mode of the space truss beam can be obtained. The frequency obtained by the energy variational method is compared with that obtained by the finite element analysis, and consistent results are found. The vibration modes obtained by those two methods are compared, and good agreement is found. The analytical solutions of energy variational method can be used as a reference for engineering design of the space truss beam.