<p>This study employs vertical normal modes method to investigate the vertical structures of cyclonic and anticyclonic eddies in the North Equatoral Current (NEC), Subtropical Countercurrent (STCC), Kuroshio Extension (KE), and Oyashio Current (OC) regions of the northwest Pacific. The vertical structure of eddies is primarily concentrated in the barotropic and first baroclinic modes, with only the first two modes needed to explain 80% of the vertical structure variations in the study region. The weight ratio of the barotropic mode in the eddy vertical structure increases from the equator to the poles, and in general, the barotropic mode ratio for cyclonic eddies is greater than that for anticyclonic eddies. Additionally, eddy vertical structures, which typically do not change sign with depth, tend to be surface-intensified in low-latitude regions but deep-reaching in high-latitude regions, with cyclonic eddies generally exhibiting greater influence depths than anticyclonic eddies. Mechanism analysis indicates that weaker stratification leads to higher barotropic mode weight ratio, deeper influence depth, and more efficient energy transfer to the deep ocean. In the study region, the eddy kinetic energy is roughly distributed as 60% in the barotropic mode and approximately 35% in the first baroclinic mode, with barotropic energy dominating in high-latitude regions and baroclinic energy being more prominent in low-latitude regions.</p>