Nuclear reactors involve a series of multi-physics coupling processes with complex interactions.With the rapid development of high-performance computing technology,the analysis based on multi-physics coupling has been paid more and more attention.Based on the multi-physics coupling platform MOOSE,the steady-state and transient multi-physics coupling simulation of Xi'an pulsed reactor is studied.The nonlinear problems in multi-physics coupling are solved by Picard iteration and Jacobian Free Newton-Krylov(JFNK)method,and the multi-physical coupling calculation of three-dimensional neutron spatio-temporal dynamics,three-dimensional solid heat conduction and one-dimensional fluid flow and heat transfer is realized.The reactor behavior under 2 MW steady-state operation and 3.45$(1$ represents an effective delayed neutron fraction)pulse operation of Xi'an pulsed reactor is calculated,and the three-dimensional power and temperature distribution of the core are obtained.The calculated results are in good agreement with the experimental results,which proves the correctness of multi-physics coupling.The multi-physics coupling method developed in this paper has the advantages of good geometric adaptability and flexible coupling,and has the potential to be applied to other micro reactors.