Abstract: As a solution to the problems of dust buildup in moisture exhaust pipeline of tobacco primary processing line, and exhausted moisture volume control, an automatic cleaning system was designed, wherein the opening of exhausted valve was fixed, the exhausted moisture volume and the negative pressure inside cylinder was closed loop controlled via a frequency conversion controller for exhaust fan motor. An automatic cleaning system for exhaust fan was designed on the basis of impeller structure and the running status of exhaust fan motor, the frequency of the exhaust fan motor was adjusted by PLC. A settling chamber was designed to separate tobacco dust from airflow and automatically clean the exhaust gas pipeline. The results showed that the volume of exhausted moisture was well controlled, the negative pressure inside cylinder was kept within (36.5 ±3.0) Pa and the frequency of exhaust fan motor was stabilized within (35 ±5) Hz. The cleaning time for exhaust fan motor and exhaust gas pipeline reduced by 132.7 min and 9.13 h, respectively, or more than 120 000 RMB yuan/year could be saved for 5 pieces of cylindrical equipment. The application of the system promotes the running stability of moisture exhaust system.