Abstract: As a key commercial species in the Northwest Pacific, Scomber japonicus has shown a decreasing population trend in recent years due to its vulnerability to marine environmental and climatic changes. Based on the fishery observation data from June to November of 2014−2021, we systematically analyzed the spatio-temporal distribution characteristics of S. japonicus and its response relationship with key marine environmental factors in the Northwest Pacific, providing a scientific basis for its resource management and sustainable utilization. The study reveals a significant seasonal migration pattern in high-CPUE (Catch per unit effort) aggregation areas: a southwest-to-northeast shift in summer, followed by a return to southwestern waters in autumn. Spatially, the inter-annual distribution was primarily between 145°E−160°E and 35°N−45°N, while monthly distribution was between 145°E−155°E and 37°N−44°N. Temporal analysis indicates a declining inter-annual CPUE trend, with monthly variation maintaining higher levels from September to November. Using a Generalized Additive Model (GAM), we quantified the synergistic effects of environmental factors, including sea surface temperature (SST), water temperatures at 100−200 m depth (T100, T150, T200), dissolved oxygen at 0−200 m water layer (DO, DO100, DO150, DO200), sea surface salinity (SSS), and chlorophyll-a concentration (Chl-a) on CPUE. The results demonstrate that temperature-related factors dominated the nonlinear effects on CPUE, with SST exhibiting the highest contribution (Cumulative deviance explained: 6.69%, p<0.001), while SSS and Chl-a showed relatively lower explanatory power. The study reveals that the spatio-temporal distribution of S. japonicus in the Northwest Pacific exhibits significant seasonal and inter-annual fluctuations, showing an expansion trend from west to east and south to north. Ocean warming may exacerbate ecological pressures on its fishery resource.