In order to improve the precision of conventional imbalanced thrust force method (ITFM), by introducing proportion coefficient n,inter-slice force inclination was determined and equation set could be established to obtain the safety factor Fs,taking both force equilibrium and moment equilibrium into account. The reliability was finally verified by several examples. Researches showed that imbalanced moment and safety factor vary near linearly when n changes. Derivation of safety factor of the method owns faster convergence speed than conventional ITFM, as well as better accuracy. Without horizontal seismic force, inter-slice force inclination is similar to the slip surface, but inclination variation mainly occurs in few rear slices of the slope while taking significant seismic force into consideration. When n=0,improved ITFM is equivalent to conventional ITFM, and consequently it could be regarded as an extension of the conventional one.
