Understanding the spatial pattern of human fishing activities is very important for fishery resource supervision and spatial management. In order to understand the spatial distribution characteristics of squid fishing vessels in the southwest Atlantic Ocean and its relationship with the marine environment, fishing effort information was calculated based on the squid fishing vessels trajectory data in the southwest Atlantic Ocean from January to May during 2018–2019 and analyzed for variation in the center of activity. The overlay maps of the spatial distribution of environmental factors and fishing effort were plotted together with three environmental data sets of the same period: sea surface temperature (SST), sea surface height (SSH), bottom temperature (BT) and chlorophyll-a (CHL-a), to investigate the relationship between the spatial distribution of fishing effort and environmental factors. The Generalized Additive Model (GAM) was used to construct a non-linear expression of fishing effort on the marine environment, and to analyze the impact of changes in the marine environment on squid fishing vessel activity in the southwest Atlantic Ocean. The results showed that the fishing effort of the boats in the study area at first increased and then decreased from January to May, and the fishing effort was the highest in February. The center of gravity of fishing boats has obvious zonal monthly changes. From January to May, the center of gravity of fishing boats shifted from north to south as a whole. The operations of squid fishing boats are mainly distributed in areas with sea surface temperature of 8–15 ℃, sea surface height of 0.14–0.16 m, bottom temperature of 5–8 ℃ and CHL-a concentration of 0.2–0.6 mg/m3 . The GAM model shows that spatial factors and environmental factors have a significant impact on the distribution of squid fishing in the southwest Atlantic Ocean. The synergy of longitude and latitude contributed the most to the explanatory variance of fishing effort. Four environmental factors, SST, SSH, CHL-a, and BT, all have important effects on fishing effort. The effects of all variables on fishing effort are non-linear. The most closely affected range of SST is 14–15 ℃, the most closely affected range of SSH is –0.1–0.02 m, the most closely affected range of BT is 5–6 ℃, and the most closely affected range of CHL-a concentration is 0.2–0.4 mg/m³ .