Abstract: At present, pressurized water reactors (PWRs) have accumulated massive long-lived high level radioactive wastes with high radiotoxicities and long decay half-life, which has long-term effects on environment and people. Since generation Ⅳ nuclear systems, including lead-cooled fast reactor, have advantages in reducing the long-lived high level radioactive wastes, a 300 MW lead-bismuth-cooled fast reactor （LBE-cooled fast reactor） design was proposed in this paper. The main physical parameters of the reactor core were modeled and calculated by using the MCNP code. Then, the accumulation of the long-lived high level radioactive nuclides was analyzed in detail and compared with the accumulation of radioactive nuclides in PWRs. The results show that productions of the minor actinides in LBE-cooled fast reactor are much less than those of PWRs, while the long-lived fission products accumulated in LBE-cooled fast reactor and PWR are almost equivalent. Overall, the total masses of the long-lived high level radioactive wastes in LBE-cooled fast reactor are less than those in PWRs, which suggests that LBE-cooled fast reactor is more competitive than PWR in reducing the long-lived high level radioactive wastes.