This paper discusses the problems in the long-term operation of vapor dryer in the No. 1 ethylene plant at SINOPEC Maoming Company including the overhigh water content of outlet cracking gas and the high pressure difference. After taking some optimization measures such as extending the constant temperature time of regeneration of the dryer V-370A from 2~4 hours to 6 hours and shortening the regeneration time of the standby dryer V-370B, the smooth operation of the plant could be maintained for a certain period of time. By replacing the molecular sieves online, the problem of drying failure caused by molecular sieve pulverization could be completely solved. According to the degree of pulverization of molecular sieves in various parts of the bed, the causes of molecular sieve pulverization and the impact of pulverization on drying effect are analyzed, and corresponding improvement measures are put forward.