Abstract: To study the formation mechanism of thermal stratification in cooling channel and its effects on the flow and heat transfer, three dimensional turbulent fluid flow and heat transfer in a regenerative-cooling channel of liquid rocket engine were numerically investigated with Reynolds stress model(RSM) model, and the coolant was hydrogen, whose thermophysical properties varied with both temperature and pressure.The results show that thermal stratification occurs at non-flow direction, the extent of thermal stratification becomes increasingly significant as the extent of heating increases, and the thermal stratification of coolant is weakened for the existence of secondary flow in throat region;the thermal stratification has little effect on the bulk temperature increase and hydrodynamic losses of hydrogen, but has significant effect on the calculation of the wall heat fluxes and temperature.