Abstract: Multi-physics coupling analysis based on FLUENT is a hot issue in current nuclear safety analysis. The reactor nuclear power calculation program (PKM) was prepared by using the point reactor neutron kinetic equations of 6 groups of delayed neutrons. The FLUENT/RELAP coupling analysis model and the FLUENT/PKM coupling analysis model were established by the external coupling method and secondary development coupling method respectively. The correctness and effectiveness of the coupled model were verified by the discharge problem of the horizontal branch pipe and the super-power transient problem of the linear reactivity introduced in a single-phase range. The coupled analysis method of the study can provide support for fluent multi-physics nuclear safety analysis.