All samples tested are extracted from West Open-pit Coal Mine of Fushun(WOPCM), Liaoning. With FTIR with reflection testing method and varied temperature, representation of functional group and thermal variation behavior of jet are analyzed. The result shows that: representation of FTIR and ATR-FTIR of Fushun jet concentrates mainly cover two areas: 2 900~2 800 and 1 600~1 200 cm-1; the absorption spectrum band of jet caused with stretching vibration ofν(CH2) becomes lower and lower along with the temperature rise in the process of low-temperature oxidation while the absorption spectrum band caused by stretching vibration ofν（CO） becomes higher and higher. Due to oxidation in the process of petrifaction, alkane in jet becomes less and less while the oxygen-containing functional group keeps on increasing, thus, the formation environment of jet consists anaerobic reduction environment.