Two self-priming pumps are used to work for mutual backup in the corridor drainage system of Luogu dam. The corridor of dam usually is flooded since the pumps have been installed, and the safety of dam has been in danger. To solve the problem, after an analysis and discussion from the experts of company, the director decides to replace the self-priming pumps by submersible pumps. By using the submersible pumps, the work reliability of corridor drainage pump has been improved obviously; the ＂unattended＂ operation mode of Luogu dam corridor drainage system also has been realized.