The calculation was carried out on flow field of supersonic turbulent duct. Two supersonic turbulent
ducts with initial area ratios 2. 0 and 3. 0 were calculated at three specific heat ratios:1. 1, 1. 2 and 1. 3. The results included the changes of total enthalpy, Mach number, pressure in duct, static enthalpy and recovery enthalpy with in crease of the cross area of duct. It shows the total enthalpy is constant in tests, but other parameters change with the increase of cross area of duct due to test materials ablation. Mach number increases with the increase of cross area,the other parameters decrease. When cross area of duct increases by 20%, Mach number increasing amplitude is less than 9%, the pressure decreasing amplitude in duct exceeds 20%, the decreasing amplitudes of static enthalpy and recovery enthalpy are within 8% and 1%. The increasing or decreasing amplitudes of parameters in duct are higher with specific heat ratio increasing and lower with initial area ratio increasing.