Abstract: An analysis on self-igniting accident of sour crude oil tank is made. The result shows that the explo- sion of tank is directly related to the FeS's self-igniting. The oxidative self-igniting comparison between HZ S saturated with vapor without oxygen and FeS prepared from Fe₂O₃, Fe₃O₄ and Fe(OH)₃, the Fe's oxides under different velocity of flow condition is carried out. The experimental results display that FeS generated in sour oil tank has a high self-igniting possibility, which reacts rapidly with oxygen in the air at room temperature, and releases heat; the velocity of flow and sulfidation time is an important influencing factor of oxidative self-igniting.