The utility model belongs to an energy-saving controller for a cotton press in the field of cotton processing. The controller consists of an external start-stop input circuit, a hydraulic pump drive motor current detection circuit, a singlechip circuit, a control output circuit, a display screen, keys and a power supply circuit. The keys input the ranges of the transformer ratio, rated current value and operation current value of a hydraulic pump drive motor into the singlechip circuit, the current detection circuit real-timely detects the operation current value of the hydraulic pump drive motor and transmits the detected value to the singlechip circuit, the singlechip circuit is controlled by a program to carry out processing and analysis, the control output circuit controls the operation of the relay of the hydraulic pump drive motor, so that the no-load hydraulic pump drive motor automatically enters into star operation, consequently, the voltage of the coil winding of the motor is reduced, the magnetic-flux-induced current is reduced, the power factor and the motor operation efficiency are increased, the active electricity consumption is reduced, and thereby, the purpose of energy saving is achieved.