Abstract: Two kinds of mixed core designs were investigated in this study respectively with partially PuThOX (plutonium-thorium mixed oxide) and U3ThOX (reactor grade ²³³U-thorium mixed oxide) loading on the basis of reference full UOX (uranium-oxide) equilibrium-cycle core design. In UOX/U3ThOX mixed core, U3ThOX fuel assemblies stay in-core for 6 cycles of which average cycle length is 5 EFPD longer than that of reference full UOX core. Compared with initial load, the fissile material inventory in U3ThOX fuel increased by 7% via 1 year cooling after discharge. Furthermore, the fuel management scheme of UOX/MOX (plutonium-uranium mixed oxide) mixed core was designed for comparison. The results show that: 1) Mixed core with PuThOX loading has similar impacts as MOX on several neutronic characteristics, such as reduced differential boron worth, reduced control rod worth, higher critical boron concentration, more negative moderator temperature coefficient, reduced shutdown margin and larger Doppler power defects; 2) mixed core with U3ThOX loading has no distinct impacts on neutronic characteristics compared with reference full UOX core.