Abstract: In order to understand the heat transfer characteristics of expander cycle regeneratively-cooled thrust chamber,three dimensional computational models of expander cycle thrust chamber were established and numerical simulation was employed.The influence of a number of factors,such as increased length of chamber cylinder,different cooling routing,different surface roughness and rib configurations on the heat transfer characteristics like coolant heat pick-up,pressure loss in the cooling circuit,wall temperature and heat flux distribution was investigated.k^-ε turbulence model was adopted for the computation.The results show that the co-flow cooling routing contributes to lower pressure loss in cooling circuit but yet lower coolant heat pick-up,when comparing with converse cooling routing.The compared results of the two uncooled ribs with different rib heights demonstrate that the increase of the heat flux is proportional to the increase of the total surface area exposed to hot gas.