The invention discloses a method for cutting rubber blanks of rubber parts of a harvester and belongs to the technical field of rubber blank cutting. A cutting device comprises a support, a transmission mechanism, a cutting mechanism, a transverse limiting mechanism, a longitudinal limiting mechanism and a rubber blank conveying mechanism. A cutting blade of the cutting mechanism is wound around a second driving wheel and a second driven wheel. An oil cylinder controls the second driving wheel and the second driven wheel to move in the vertical direction through a plunger. A transverse limiting air cylinder of the transverse limiting mechanism drives a first limiting block to be close to a second limiting block. Longitudinal limiting air cylinders of the longitudinal limiting mechanism control pressing plates to move in the vertical direction. A conveying air cylinder of the rubber blank conveying mechanism drives a base to move through a pushing rod. According to the method for cutting the rubber blanks, cutting, transverse limiting, longitudinal limiting and rubber blank conveying are controlled through the oil cylinder or the air cylinders. Batch cutting of the rubber blanks is achieved, and the automation degree is high; and the cut rubber blanks are small in size error.