Abstract: The method of critical slip field for slopes is newly developed by Prof. Zhu Dayong. The unbalanced work is defined as the difference of virtual work of loadings to inner energy dissipation and the new method of critical slip field in terms of energy is presented. This new method includes two calculating steps, i.e. the determination of slip surface yielding the maximum unbalanced work with regard to given factor of safety and the determination of minimum factor of safety, under which the maximum unbalanced work is zero. Two typical soil slopes are analyzed by using this new method and the comparison of results proved its validity. This new method is characterized by simplicity of calculation and the avoidance of assumption on inter-slice forces.