Abstract: Variable fertilization technology is an important part of the precision agriculture technology. Because fertilizing machine is driven by hydraulic motors, in this paper, a variable fertilization controller based on MCU was presented under the corresponding way. The controller receives orders from the field-computer through the RS232 serial port. After it carries on analysis processing, it generates the corresponding I / O port signal to control the action implementation by the driving amplification circuit. At the same time, the use of vehicle speed sensor and magnetoresistive sensor collect the speed information through the exclusive sampler. The information feedback controllers in order to achieve closed-loop control. Results show that the design of the variable fertilizer controller is suitable for the variable-operating requirements.