Based on the thought of conservation of energy, using the modeling method of radial slice method, assuming a virtual displacement, a mathematic model of landslide stability calculation is established, so as to provide a new method for landslide stability analysis. Based on the virtual displacement ds, the gravitational potential energy change △U and the friction energy dissipation △W on sliding surface are deduced; and then the landslide stability coefficient is defined as Sc = △W/△U; finally, the mathematic expression of landslide stability coefficient Sc is obtained in two cases of considering groundwater and without considering groundwater. Through the example analysis, and comparing the calculation result with Janbu method. The results show that, without considering the groundwater, calculation results of energy method and Jianbu method is relatively close; and the former stability coefficient is slightly higher; the differential ratio is 0.19%; under the condition of considering the influence of groundwater, the differential ratio is 9.77%; the stability coefficient calculated by energy method is lower; namely, in the energy method, the influence of groundwater on landslide stability coefficient is greater. Based on example 1, the main parameters of the model are analyzed on the sensitivity of the stability coefficient of Sc. Finally, the similarities and differences between the energy method and JianBu method are essentially contrasted.