The invention relates to a slow pulling mechanism of an ultrasonic washing unit. The slow pulling mechanism comprises a driving motor, a first conveyor chain, a second conveyor chain, a lifting and pulling chain and a supporting table which are arranged on a support. The driving motor drives a rotating shaft through the second conveyor chain. A first chain wheel of the first conveyor chain is arranged on the rotating shaft. A transverse shaft of the supporting table is fixedly connected with one side of the first conveyor chain. The supporting table is connected to a guide rail of the support in a sliding mode. The upper end of the supporting table is fixedly connected with one end of the lifting and pulling chain. The other end of the lifting and pulling chain is fixedly connected with a balancing weight. The chain conveying structure and the balancing structure are adopted, and therefore slow-speed and uniform-velocity lifting and pulling are achieved for sheet glass, water drops or water bubbles on the surface of the sheet glass are effectively eliminated, water spots or bubbles are prevented from being left in the subsequent drying and packaging process, the washing effect is improved, and the defective rate is decreased.