To investigate the effect of regenerative cooling channel geometry on pyrolysis of endothermic hydrocarbon fuel, a series of supercritical pyrolysis experiments of n-decane in the rectangular and circular tubes were conducted. Moreover, sensitivity analysis of production of propylene and methane as well as CFD simulation were also done. The results showed that gas yield and conversion in the circular tube with an inner diameter of 2 mm had a sim-ilar tendency with the one of 1.5 mm in inner diameter. The conversion in the circular tube was much less than that in the rectangular tube at the same outlet temperature. The heat sink of the rectangular tube at the same out-let temperature was larger than that of circular tubes, but the temperature at the cer of the rectangular tube was relatively high. According to the experimental data of the test tubes, a correlation between the conversion and the temperature in the rectangular and circular tubes at the same outlet temperature was fitted, providing a reference for the design of regenerative cooling channels.