To study the effects of dissolved oxygen concentration on thermal oxidation coking of Chinese RP-3 aviation kerosene, a deoxygenation device and an on-line measurement device are designed and built. The coking amounts at different initial dissolved oxygen concentrations are measured, the morphology and elemental compositional analysis of coking deposits are analyzed by scanning electron microscope and energy disperse spectroscopy. By varying the heating length of the electrically heated tube, the distribution of the dissolved oxygen concentration along the tube is also measured. The experimental results suggest that lower initial dissolved oxygen concentration leads to less thermal oxidation coke. When the initial dissolved oxygen concentration decreases from 70.0 ppm to 22.4 ppm and to near 0 ppm, the total coking amount reduced by 47.6 and 75.4%. But at the oxygen-starved condition, the coke is not completely eliminated, and its surface morphology is obviously different. The dissolved oxygen concentration shows a declining trend along the tube, and it decreases dramatically from 39.3 to 4.5 ppm at the axial position of 40–50 cm. The measuring results along the tube indicate that thermal oxidation coking is affected by both temperature and dissolved oxygen concentration, but the sensitivities are different at different stages.