Abstract: Simulation experiments were carried out on the simulation test facility for nuclear seawater desalination reactor, and the performance of the passive residual heat removal from the core was presented. Numerical model was built by RELAP5/MOD3.2 code to simulate the influence of natural circulation establishment and the residual heat removal with different initial water levels in accumulator tank. It is shown that the RELAP5/MOD3.2 code can well simulate the passive residual heat removal process of the passive safety facility of the seawater desalination reactor, and the calculation results of the code are well accordant with the experimental results.