Abstract: In the shielding calculation of nuclear facilities, the deep penetration in large shielding space has always been one of the difficulties in the application of Monte Carlo program. In this paper, based on NUREG/CR-6115 PWR fluence rate calculation benchmark issued by NRC, cosRMC was used for fine modeling, and the results were compared with those of reference program. In the calculation process, the variance was reduced by setting regional importance to improve the calculation efficiency. The calculation results show that the relative deviations of neutron flux density and photon flux density between cosRMC and reference programs at different penetration depths are within plus or minus three times of the statistic errors, which is in good agreement, and verifies the correctness of cosRMC in shielding calculation and deep penetration problem. The effects of different electron processing methods on the photon flux density were also compared. The results show that the photon flux density is underestimated by at least 6% when electrons are not taken into account, and the thick-target bremsstrahlung model of cosRMC program electron processing is in good agreement with reference program.