The thin film evaporator consists primarily of a heating jacket, an internally rotatable wiper, and a condenser and vacuum system. In the high vacuum system, the feeding liquid is fed from the upper part of the evaporator. After that, under the driving of the gravity and the rotating wiper, a downwardly swirling film is formed along the inner wall surface of the jacket. The finishing fluid is discharged from the bottom discharger, while the steam is discharged from the upper part. The system is very suitable for liquid materials with high viscosity, easy crystallization, easy scaling, suspended solids or heat sensitive properties, and is widely used for pretreatment and finishing of products in the chemical, pharmaceutical, health care and other industries.