The sealing plug type and the structural design of cylinder oil discharge valve of runner of a Kaplan turbine were unreasonable,oil leakage phenomenon was caused after the installation.The discharge valve and plug of sealing type and plug structure of the Kaplan turbine were improved,the problems were solved of the plug unable to reach pretightening force and sealing fracture.The practical application shows that the improved sealing structure can prevent the cylinder oil leakage,the plug of discharge oil valve can be easily tightened to designed torque and is easy for disassembly and disassembly.