To address the limitations of traditional ultrasonic nondestructive testing techniques, which often have detection blind spots and cannot simultaneously detect both surface and internal defects in test specimens, a novel Electromagnetic Acoustic Transducer was designed based on the principles of electromagnetic ultrasonics. This EMAT can simultaneously generate Rayleigh and shear waves, enabling concurrent detection of surface and internal defects in specimens. A rayleigh-bulk wave composite EMAT simulation model was developed in COMSOL to analyze the generation mechanisms of the composite ultrasonic waves and their interactions with defects. The composite EMAT was designed and fabricated, and an electromagnetic ultrasonic signal detection system was established. Detection and localization experiments were conducted on custom aluminum alloy specimens containing surface and internal defects. The results indicate that the designed rayleigh-bulk wave composite EMAT effectively detects both surface and internal defect echoes, achieving a localization error of 0.48% for surface defects and 0.7% for internal defects.