Abstract: Based on the 3 000×10³ t/a heavy oil catalytic cracking unit of Lanzhou Petrochemical Company, the operation status of the reaction-regeneration system disengager VQS, single-stage cyclone separator, and the first and second stage cyclone separators of the regenerator were analyzed. The relevant operating conditions during the operation period of the device were collected and compared, combined with the inspection and maintenance of the device during the previous major overhauls, it was judged that the working performance of the above gas-solid separation equipment showed the phenomenon of separation efficiency decline and operating conditions deterioration, and the main reasons of the separation efficiency decline included the deformation caused by the long-period operation of the equipment. Damaged and internal damaged parts could not be fully inspected and repaired, and the main problems that affected the long-term operation of the device caused by this, included the wear of the slurry pump, the increase of coking, the loss of catalyst, the wear of the flue gas turbine and the fouling of the blades, and the boiler tube bundle dust and so on. The settler VQS, single-stage cyclone separator and overall replacement of material legs, regenerator first and second cyclone separators and overall replacement of material legs were proposed and implemented. In the new operation period of the device, the above-mentioned gas-solid separation equipment operates well, and the catalyst is efficiently separated, completely eliminating the bottleneck of the device production.