Steel epoxy sleeves have found extensive applications in the repair of damage in oil and gas pipelines, and the bonding quality of the resin layer is crucial for the reinforcing effect after repair. In this paper, a method for inspecting the bonding defects in steel epoxy sleeves utilizing Circumferential Shear Horizontal (CSH) guided waves generated by Electromagnetic Acoustic Transducers (EMATs) was proposed. Firstly, the propagation characteristics of CSH0 mode guided wave in the steel epoxy sleeve were studied by establishing a finite element model. Secondly, the feasibility of using CSH0 mode guided wave to detect step-type through-cavity defects pre-made in the bonding layer of the steel epoxy sleeve was explored through a combination of finite element simulation and experimental research. Both simulation and experimental results consistently indicate that the amplitude of the direct wave of the CSH0 mode is basically linearly correlated with the cavity width. This suggests that the method can effectively detect through-type cavity defects in the bonding layer and distinguish their sizes. This verifies the feasibility of the proposed method for detecting bonding defects in steel epoxy sleeves.