Abstract: According to some assumptions, the dynamic mechanical model for slope anchorage system is established for free vibration. Some formulas for the natural frequency and the corresponding vibration modes of anchorage system are deduced. Compared to that of the other methods, the feasibility of the theoretical formulas is verified through a specific example. Meanwhile, the natural frequency of slope anchorage system is analyzed under the influence of different parameters, anchor length, equivalent lumped mass and stiffness coefficient . The inherent laws between them are discussed. It is found that the anchor length and the value of stiffness coefficient have less effect on the low-order natural frequency, and their impact on the size of high-order natural frequency is larger. The equivalent lumped mass has less effect on the natural frequency of slope anchorage system. The slope anchorage system has the natural frequency of linear vibration mode under certain conditions.