Abstract: From the long-term point of view, the breeding capability of the super fast reactor (SCFWR) is an important issue. SCFWR has the potential for proliferation, for the reason that the coolant density of the supercritical water reactor is only equivalent to 1/3 of that of the current boiling water reactor (BWR), coupled with the grid layout. In order to explore the proliferation of SCFWR, a multi-group 3-D diffusion core calculation methods based on the finite difference method were used. And a series of examples with different factors on the proliferation of SCFWR, such as, the core coolant flow type, the use of stainless steel and ZrH_1.7, the type of reactor layout, fuel rod size, the share of PuO₂ in the MOX, core burnup and core size, were calculated. As can be seen from the results, there are several ways to get greater core conversion ratio: adopting convection flow pattern, adding ZrH_1.7, adopting the appropriate core layout, increasing the fuel rod diameter, increasing the share of PuO₂ in the MOX and increasing the size of the core to decrease the core leakage and so on. The results of those calculations provide a reference basis for improving conversion ratio of the SCFWR.