One hundred kinds of tractors produced by 6 main domestic tractor manufacturing enterprises were studied. The vertical, pitch and heave vibration natural frequency of the domestic tractors’ vibration system were calculated theoretically to provide a basis for the design of domestic tractors’ damping system. The method of tractor moments of inertia determination proposed by Dworecki Z et al and the approximate calculation formula of tractor tire stiffness obtained by experimental method proposed by J.A.Lines and K.Murrphy were used in the calculation of natural frequency. In order to estimate the accuracy of the calculation result ,the test was conducted. The results showed that the method of calculation was reliable. The conclusion in this paper shows that the natural frequency of domestic tractors’ vibrating system in vertical, pitch and heave direction is concentrated in 3Hz~4Hz, 2.8Hz~3.8Hz and 2.9Hz~3.9Hz respectively. The natural frequency in three directions will decrease with the increase of the rated power. At the end, the formulas for calculating the natural frequency of domestic tractor in three direction have been brought out. During designing the damping device of tractors, the formulas can be used for estimating the natural frequency of the tractors’ vibrating system.