Handling stability is one of the important active safety performances of automobiles, and it is the most critical performance that affects the safety and stability of automobiles during high-speed driving. Based on a linear two-degree-of-freedom automobile model, this study investigates the factors affecting the handling and stability of medium-sized cargo automobiles and calculates and analyzes the steady-state response, transient response, and frequency response of the automobiles under certain operating conditions of empty and full load. By increasing the tire lateral stiffness (25% to 35%) and the automobile stability factor, the handling stability system parameters of the automobiles were optimized. Further analysis and verification show that under empty and full load conditions, the gain of automobile yaw rate decreases by 23.1% to 35.6%, the natural circular frequency of yaw rate fluctuation increases by 23.5% to 47.1%, the amplification ratio at resonance decreases by 64% to 78.9%, and the phase lag angle decreases by 31.6% to 46.2%. The system performance optimization effect is significant.