Abstract: The centrifugal pump leakage from enlargement of the entry sealing ring clearance can destroy facility performance and result in extra energy consume, so there is demand for overhaul. In view of entire economy benefit, an economy model is built to ascertain optimum overhaul occasion based on condition monitoring. Firstly, the effect of sealing ring clearance on the performance curves is analyzed, and based the measured data of condition monitoring the changed performance curves are obtained with the extra energy consumption. Secondly the economy model for centrifugal pump inner leak is set up from the view of maintenance cost per month and extra energy consumption. Finally, the instance results show that this model can predict optimum maintenance time briefly, and the total economy performance can also be raised.