Abstract: Radiation slices method has more advantage than other slice methods in dividing slices. But currently the radiation slices method applies only to the type of circular sliding surface. The method using radiation slices to calculate factor of safety (FOS) is not as completion as those of other slices methods. This paper presents a radiation slices-division mode for arbitrary curved slip surface. Radiation soil slice is taken as a uni. Direction of the inter-shear force uses two different types of the directions based on the previous results. Then the strict balance equation of force and torque is established. The formula of FOS for the general assumption of inter-force is deduced. When using the inter-force assumptions of Sarma and M-P method, their applicability to the radiation slices method is studied. At the same time, in order to broaden the use of M-P method in the radiation slices method, two new inter-force assumptions are put forward based on the inter-force relationship of M-P method by analyzing the inter-force relationship between radiation slice and vertical slice. When the sliding surface (including circular and arbitrary curve) is fixed and the number of slices is different, this article researches the feasibility of above-mentioned methods and through comparing and analyzing some examples. The results show the follows. (1) When the direction of inter-shear force is the first case of direction, the inter-force assumptions of Sarma method and the three kinds of M-P methods could be all applied to the radiation slice method for analyzing slope stability. (2) The two new kinds of inter-force assumptions based on M-P method have better improvement in convergence of calculated results than the traditional inter-force assumption of M-P method. (3) In the radiation slice method, arbitrary sliding has more applicability than the circular sliding surface.