To address the issues of poor stability, low steering control resolution, and severe soil damage caused by unilateral braking steering in the automatic steering control of a single hydro static transmission（HST）tracked tractor, a differential steering control system based on state feedback was proposed. Firstly, the mechanism of differential steering using a single HST was analyzed. Then, based on the kinematic model of the tracked tractor, a differential steering control method using pulse width modulation（PWM）was designed. This method improved steering control resolution and stability by precisely adjusting the stroke of the steering hydraulic cylinder. Next, a control system was developed with an STM32F4 microcontroller as the core, which integrated both linear path planning and steering control, completing the design of the onboard controller. Finally, field tests were conducted under three speed conditions on both cement and field surfaces. The test results showed that at speed of 2 km/h, 3 km/h and5 km/h, the mean absolute errors of straight-line tracking on the cement surface were 1.6 cm, 2.2 cm and 3.1 cm, respectively, with standard deviations of 2.7 cm, 2.9 cm and 3.6 cm. On the field surface, the mean absolute errors were 1.7 cm, 1.9 cm and 2.9 cm, with standard deviations of 2.2 cm, 2.1 cm and 3.4 cm, respectively. These results demonstrated that the system outperformed traditional unilateral braking steering in various environments, significantly improving steering accuracy and stability.