in our country, the pump stations have played a great role in the water transfer, water supply, and flood control, drought relief since the 60s of the 20th century. But the frequent malfunctions of the water pumps have threatened the safety, stability and economic profits of the pump stations. This paper studied the On-line Monitoring and Trouble Diagnosis of the Large-size Pump Set, aims at transferring the conditional “planned overhaul” to “Condition-Based Maintenance”, it can find fault and avoid accidents in time, reduce the production cost.