Abstract: The physics properties and thermal-hydraulic characteristics of liquid-fuel molten salt reactor are different to that of solid fuel reactor, and the effect of liquid fuel flow must be considered when the analysis code used in solid fuel reactor analysis will no longer be directly applied. Considering the fuel flow effect of the reactor, the neutron dynamic model based on particle conservation equation coupled with molten salt fuel flow and heat transfer models was derived and a three-dimensional neutronics/thermal-hydraulics coupled code was developed. The physics and thermal-hydraulic characteristics of MOSART in steady state were studied. The calculation results indicate that the fuel flow has minor effect on neutron distribution, but major effects on the delayed neutron distribution and temperature distribution in the core.