Control method and system for engine speed

The invention provides a control method and a control system for reducing engine speed. The method includes the following steps: an operation condition distribution diagram of an engine is obtained; the operation condition distribution diagram includes a plurality of units; current demanded revolving speed, required torque, operation revolving speed, and operation torque of an engine are obtained;a first unit corresponding to the demanded revolving speed and the required torque and a second unit corresponding to the operation revolving speed and the operation torque are obtained in the operation condition distribution diagram; and output revolving speed of the engine is controlled based on a relationship between the first unit and the second unit, and amount of slip of a clutch is controlled. According to the method of the invention, operating conditions of the engine are divided into several areas, control of the amount of slip amount is separately performed on the areas to reduce vibration and noise of a ve