Abstract: Research on the steady characteristic of passive residual heat removal system（PRHRS） for Chinese advanced PWR has been performed in a systematic way.A total of 237 sets of test data at steady state have been obtained and the main influence factors,for example,system pressure,height between heat resource and heat sink,system effective resistance coefficient,and wind velocity,on the two-phase natural circulation flow rate and residual heat removal capability were identified.On the basis of theory analysis,steady correlation of two-phase natural circulation has been obtained.Relative errors of 95% test data were less than ±16%.There is a considerable effect of system state parameter（such as system pressure and valve form resistance coefficient） and system boundary condition（such as environmental temperature and chimney height） on the threshold of elevation between heat resource and heat sink,and its correlation of two-phase natural circulation system has been obtained.Steady characteristic research shows that the PRHRS has the capability of removing the core decay power（2% full power） through natural circulation.