With the widespread adoption of silicon carbide (SiC) inverters in high-performance electric vehicles, the associated high-frequency switching characteristics have significantly intensified the issue of interturn transient overvoltage in permanent magnet synchronous motor (PMSM) hairpin winding. This phenomenon has become a critical factor affecting the insulation lifespan and operational reliability of the motors. The coupling effects of fast switching transients, long cable transmission paths, and the unique structural parameters of hairpin winding result in a distinct voltage stress amplification effect across winding turns. These high-frequency transient phenomena increasingly challenge traditional design and protection approaches for motor insulation. To comprehensively address this emerging reliability concern, this study adopts a multi-method research framework that combines equivalent circuit modeling, high-frequency parameter identification, and time-domain electromagnetic transient simulation. The transient overvoltage propagation mechanisms, spatiotemporal distribution characteristics, and dominant influencing factors of interturn voltage stress are systematically investigated and quantitatively analyzed. The findings offer valuable theoretical insights and practical engineering guidance for insulation design.