Abstract: In order to effectively control the decay degradation of engine lubricating oil during actual use, the paper combined hierarchical recognition theory into recognition of the actual use factors on degradation of engine lubricating oil. Through constructing the index system and hierarchical diagnosis structure diagram of influencing factors on the degradation of engine lubricating oil and matrix utilizing hierarchical judgments, the paper identified main actual use factors that influence the degradation of engine lubricating oil. The results show that temperature is the major influencing factor in constituting lubricant degradation, and the engine condition changes and external environment will also have certain effects on lubricant degradation.