Abstract: A coupling interface between Monte Carlo neutron transport code JMCT2.2 and commercial CFD code FLUENT was developed by C++ language. The one-by-one mapping strategy that one cell in the MCNP model logically corresponded to the computational domain in the FLUENT model was used in this coupling method to realize simple partition of the physical model and refinement of partition of CFD mesh. The calculated results of a PWR single cell model and a PWR 3×3 fuel model were compared between this program and the MCNP-FLUENT program to validate its accuracy. The results demonstrate that this coupling method between JMCT code and FLUENT code is reasonable and it can accurately calculate the feedback parameters.