Abstract: In order to solve the problems of small adjustment range and uneven seeding of traditional wheat seeder, this paper designs an electric control system of automatic seeding adjustment based on PLC control. The system is composed of PLC controller, speed sensor, stepping motor and so on, which replaces the traditional ground wheel and side box mechanical driving mode. Its main working principle is to install the speed sensor on the inner side of the driving wheel of the tractor. When the speed sensor collects the speed signal of the tractor, it sends it to the PLC. After calculation and processing, it sends the corresponding control signal to the stepper motor. The stepper motor adjusts the speed according to the control command, and drives the seed metering shaft of the external grooved wheel seed metering device to rotate, and the speed of the seed metering shaft changes, The number of seeds in the metering wheel changes accordingly, so that the sowing amount of wheat is adjusted. The experimental results show that this method can effectively control the wheat seeding error within 5% per mu, and the sowing uniformity coefficient is less than 40%, which can meet the needs of wheat precision sowing and achieve the purpose of reliable and efficient operation of modern agriculture.