The utility model discloses a power saving device for fluid pump, including sampling wheel, test probe, fixed bolster, singlechip and display alarm device, the sampling wheel circumference outside evenly is provided with boss and recess, and the boss surface is provided with anti - light -absorbing coating, and the recess is provided with inhales light -absorbing coating, test probe is the fiber optic probe, and fiber optic probe one end is passed through optic fibre and is connected with light source generator, and fiber optic probe other end passing signal line connection signal receiver, signal receiver connect gradually impulse generator, signal amplifier, guard grating, converter, converter to be passed through the port and connect power source and fluid pump motor interface, the sampling wheel is fixed at the fluid pump epaxially. The utility model discloses an on line measurement utilizes fiber optic technology, improves the precision of tachometry to can the real time transport rate signal and carry out the regulating controlling and reach the economize on electricity effect.