After opening the No.2 lowpressure cylinder for overhauling a 600 MW su percritical unit, the vibrations of the cylinder and generator exceeded the values before overhauling and the alarm threshold value. The data analysis shows that t he change of bearingload distribution due to adjusting alignment is the main r e ason resulting in serious vibrations. In order to saving the repair time, the fi eld h olobalancing is used for damping the vibrations of all bearings to standar d limits.