With the wide application of screw compressors, lubricant coking from improper maintenance is increasingly common. Coking reduces efficiency and may cause rotor seizure, leading to major economic losses. This article analyzes the physicochemical mechanisms of coking, identifying oxidation, metal catalysis, water contamination, and residual old oil as direct triggers. However, the root causes are human factors – including insufficient professionalism of oil producers and user errors such as mixing oils, using inferior substitutes, and ignoring accessory quality. The article provides systematic prevention measures: using specified oil, cleaning the oil circuit before each change, selecting high-quality air filters (with simple test methods), and maintaining unobstructed cooling systems. This paper offers maintenance personnel actionable solutions to eliminate coking at its source and ensure long-term stable compressor operation.