The eddy current pulsed thermography is a new technique for defect detection with high detection speed, high sensitivity, and large detection range. To adapt the dynamic detection of wheel tread, this article proposes a rectangular electromagnetic induction excitation sensing structure. By deducing the mathematical model of the magnetic circuit of the sensor structure, the feasibility of the sensor structure is proved theoretically. Through numerical simulation, this study analyzes the distribution of electromagnetic and eddy current field in the cracked area of tread surface. And the detection results of the straight coil are compared. Based on this, an automatic wheel flaw detection system is established, which is capable of dynamic measurement of defects at 65 mm/ s speed. The results show that, by optimizing the induction heating uniformity of the wheel tread, the rectangular yoke sensing structure improves detection results for fatigue cracks in the shallow surface of the wheel tread (axial surface opening).