To reduce water usage and :wastewater., treatment in coal gasification processing, the use of non-aqueous quenching agents was proposed. The purpose of this stud to assess the potential of-using coal tar as a quenching agent for the Luger coal gasification. A low-temperature gasification-derived coat tar and an ethylene tar obtained from the petroleum naphtha cracking process in ethylene production were subjected to thermal aging tests to determine the effect of thermal severity On their viscosity and chemical composition. The viscosities of coal tar and ethylene tar as a function of the aging time were similar and relatively constant at 200 degrees C. At 250 degrees C, the coal tat was More unstable and had a shorter viscosity increase onset time than the ethylene tar. The tar samples before and after thermal aging tests were subjected to gas chromatography mass spectrometry (GC MS) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to determine the molecular composition. The results indicated that olefins, especially aromatic olefins in the coal tar, were unstable, winch likely caused polymerization of,coal tar species during thermal aging, and. resulted in a short viscosity increase onset time. By adding a polymerization inhibitor, the viscosity increase onset time of coal tar was prolonged. The coal tar is potential for use as a quenching agent for coal gasification.