Abstract: One important character of next generation PWR is fuel enrichment. Taking into account of fuel fabrication and burnup, the ²³⁵U enrichment in UO₂ fuel is less than 5%, and the content of fissile Pu in MOX fuel is also less than 6% in general in PWR. The enrichment in the next generation fuel is likely to exceed the existing standard and the average burnup is expected to reach 70 GW•d/tU, which proposed new requirements for reactor calculation software. The fission reaction rate distribution, neutron flux density distribution and nuclear number density with the burnup for the next generation PWR fuel pin cell and fuel assembly were analyzed using cosRMC. In addition, the burnup of Gd rod was also analyzed in detail. The results show that the result using cosRMC agrees with that calculated by other well-known codes. It is also shown that the difference of Pu content in fuel calculated by different codes increases with burnup.