Abstract: This paper presents the condensed mode transition operation when static electricity is not very stable in the reactor during starting up of the UNIPOL polyethylene unit. The commercial application indicated that through working out a good technological programme，formulating a detailed transition procedure, and keeping close watch over operation,the condensed mode was successfully established even if water was injected into the reactor to control static electricity at the beginning of start-up. As a result,the reactor start-up was smoothly implemented and steady production of the unit was achieved quickly.