Measuring the ground speed is important for a variable rate fertilizer machine. Since the working environment is hard, the reliability and antijamming capa bility of the ground speed collecting system is poor. A ground speed collecting system for a variable rate fertilizer machine is developed based on Bluetooth. A n ARM microprocessor is used to receive input signals from the ground speed sens or, a photoelectric encoder set on one of the wheels of the machine. and calcula te the working speed. And then the working speed signals are transformed into th e Bluetooth signal format, and transmitted to variable rate fertilizer controlle r by the KC111 adapters. The maximum error of the test is 292%. It shows that the developed system is practical.