After long-term overseas construction, hydraulic oil is prone to foaming, turbidity and emulsification. Most operators only replace oil blindly without locating root causes, resulting in repeated faults and continuous efficiency loss. Hydraulic oil foaming is mainly caused by air intake, insufficient oil level and blocked filters; oil turbidity and emulsification result from water mixing, expired oil and mixed use of different oil models. Troubleshooting methods include checking pipeline tightness for air intake, supplementing standard hydraulic oil for low oil level, replacing blocked filters and draining emulsified oil with thorough tank cleaning. Targeted root cause treatment and regular oil inspection completely eliminate hydraulic oil abnormalities and stabilize power output.