Flue gas turbine unit is one of the key equipments in catalytic cracking unit, its operation quality and operation cycle working length have important roles in guaranting the full load operation, reducing energy consumption, extending the operating cycle.The orginal YLII 8000B model flue gas turbine in 2FCC of SRCC refinery has piled up a lot of catalysts between the first and second roulette seriously, which impacted on the long-term operation of the flue gas turbine. Various factors affecting the long period operation were analyzed, the key factors of downtime were found, the flue gas turbine was reformed and operation situation was analyzed. The problem of the rotor dynamic unbalance situation caused by catalyst packing was solved after reformation.