Abstract: Through the calculation of the fuel average discharge burn-up of HPR1000, the isotope of Pu in the spent fuel has been derived, with which composition the MOX fuel shall be designed. Based on the discrete fuel module design, the power gradient with the fuel module of UO₂ is reduced through the discrete layout of MOX fuel bar with Pu contents. This paper employs Monte Carlo Program MCNP and COSLATC to simulate the reactor core power distribution and the thermal neutron flux distribution, and uses the compartmentalized and layering loading scheme with low leakage to reduce the power gradient between fuel modules and flatten power distribution of the reactor core. Leaving out burnable poisons, three MOX modules with different Pu contents are used to control the power peak factor of the mixed reactor core at around 1.77, visibly better than the power peak factor of the original reactor core, which serves to provide a scheme of considerable reference value that introduces the MOX fuel for the 3rd generation of domestically developed pressurized water reactor in China