In the field of agricultural spraying, precise adjustment of electromagnetic valve flow is an important role to achieve variable spray. Due to mechanical inertia and electromagnetic inertia during the operation of solenoid valve, the response of solenoid valve is delayed. In order to improve the linear range of solenoid valve, a flow controller of solenoid valve was designed based on BOOST circuit by using the inductance characteristics of solenoid valve. Firstly, the hardware circuit of the controller was completed, including microcontroller unit, pulse width modulation (PWM) generator and solenoid valve drive circuit, and the appropriate energy storage capacitor was selected to store the output high potential of BOOST circuit. Secondly, the solenoid valve driven by double voltage did not need additional power supply voltage conversion circuit. By precisely controlling the high frequency onoff mode of the solenoid valve, it realized high voltage opening, low voltage and high frequency maintenance of conduction, and fast release of energy when closing. In the maintenance mode, fuzzy control algorithm was used to set the duty cycle of maintaining on mode, which ensured that the energy storage capacitance can provide enough power for accelerating opening mode. With the help of the spray flow acquisition platform, the flow data under different pressures (110kPa, 180kPa, 250kPa, 320kPa and 390kPa) and duty cycles (3%~97%) before and after the improvement were tested. The results showed that under the five pressures, the improved linear range of flow was increased from 10%~92%, 10%~92%, 10%~92%, 10%~92% and 8%~92% to 4%~92%, 4%~94%, 4%~94%, 4%~94% and 3%~94%, respectively. The designed solenoid valve flow controller based on BOOST circuit had wider flow liner range than the commonly traditional method.