By analyzing the problems in a power plant,as the low pressure (LP) safety oil pressure often reduced after the turbine unit start to work and the turbine tripped in the process of the oil filter switching,it was pointed out that the main reason of the LP safety oil pressure frequently to reduce was the poor quality of oil,and the reason of oil pressure fell sharply in the process of LP safety oil filter switching was the wrong operation steps.By strengthening the management of oil quality and modified the operation steps of LP safety oil filter,the safe operation of the unit was ensured.