Abstract: Due to some shortcomings, the usual piezoelectric ultrasonic, eddy current, magnetic flux leakage, machine vision and other surface inspection methods cannot meet the rail head shallow surface defects detection requirements.In this paper, the air-coupled ultrasonic Rayleigh like wave detection method is used to evaluate the shallow surface defects of the rail head by using the change of the amplitude of the echo signal at different frequencies and different defect depths. Through the simulation and experimental research on the air coupled ultrasonic guided wave detection process, the feasibility and reliability of the detection are proved.