[en] One design of the passive residual heat removal (PRHR) system of nuclear reactor was presented. The PRHR system removes the residual heat of reactor to heat sink by natural circulation of three loops under accident condition. To verify the ability of the PRHR system, RETRAN02 code was used. Reference to the MUTSU parameters, numerical calculation simulating the residual heat removal under 100% rated condition was carried out for the system design. And several key factors affecting the capability of residual heat removal were analysed