High-tensile bolts are critical components in key structures such as suspension bridges and wind turbine towers, where the quality of their installation significantly impacts the stability and safety of the entire structure. However, traditional torque methods struggle to accurately measure the axial preload of bolts, making it difficult to assess structural stability effectively. To address this issue, a bolt axial force detection system was developed based on the Acoustoelastic effect, incorporating circuits such as high-voltage excitation and voltage-controlled gain. The system detects echo signals through an excitation piezoelectric sensor and utilizes a cross-correlation algorithm to calculate the time-of-flight difference, which reflects the stress state of the bolt. Stress-transition time calibration experiments were conducted, along with comparative testing between the ultrasonic and torque methods for wind power bolts. The experimental results indicate that when the axial preload of a bolt reaches 40% of its rated value, the system achieves a stress measurement error rate of ≤2.81%, with a resolution of up to 0.250 7 kN. This meets the requirements for accurate axial preload measurement. Compared with the traditional torque method, the ultrasonic approach demonstrates a clear advantage in reducing measurement error and improving resolution during bolt service, offering a reliable technical solution for stress measurement in industrial applications.