Abstract: The coking characteristics of endothermic hydrocarbon fuel S-1 on Ni-Cr alloy was studied in a laboratory-scale continuous flow reactor system. The carburation on alloy was proved by EDX analysis. The composition of cokes was determined by element analysis (EA), which showed that the ratio of hydrogen and carbon of the coke decreases soon with the extending of reaction time. Surface morphology of coke was determined by means of scanning electron microscopy (SEM) after heat treatment at the temperature from 700 ℃ to 1 200 ℃ with heating rate of 20 ℃/min by Differential scanning calorimetry (DSC). The results show that temperature has an important effect on the structure of cokes. The analysis results of soluble coke show that intermediate coking product consists of aromatic compound and paraffin.