Abstract: To understand the complex fluid flow and heat transfer in heater nozzle, three dimensional fluid/solid coupled heat transfer method was employed. Governing equations for hot gas, solid wall and coolant were established respectively, radiation heat was added into the energy equation as a source of heat radiation. Firstly the heat transfer of the AEDC（arnold engineering development center）  nozzle was simulated in this method; the coolant temperature rise and the heat flux distribution were found to agree very well with the experimental results. This shows the coupled method is valid in solving conjugate heat transfer problem. Then the method was used to analyze the heat transfer in heater nozzle of a scramjet test facility. When the water flow rate is 2.0 kg/s，the heater nozzle is well worked. The effect of the radiation heat cannot be ignored.