In order to explore the impact of climate change on fishery resources, using the 2008—2017 Argo grid data (BOA_Argo) and the fishing log data of commercial fishing vessels during the same period, the temporal and spatial characteristics of the thermocline in the main fishing grounds of the yellowfin tuna purse seine in the western and central Pacific Ocean in La Ni’a and El Ni’o years were studied. Combined with GAM (generalized additive model) model, the variables affecting yellowfin tuna were analyzed. The results showed that, in the La Ni’a year, the CPUE moved westward as the high-value zone of the upper bound contracted westward, up to 145°E, and in the El Ni’o year, the CPUE was moved eastward to 165°E. Compared with normal years, the upper boundary depth difference of the thermocline on the east and west sides of the equatorial Pacific was larger than that of the normal year, and the upper boundary depth of 80~130 m was westward. The strength of the thermocline was generally weak in the west and strong in the east. The thickness of the thermocline was based on 15°N and 15°S, and each had a thick band-like distribution structure. The CPUE was distributed in 120—200 m thick. When the temperature range of the upper boundary of the thermocline was 27.5~29.5 ℃ and the intensity range was 0.08~0.13 ℃·m-1, the CPUE distribution was denser. The upper-bound temperature had the greatest impact on the CPUE. The eastward shift of the CPUE in El Ni’o and the westward shift of the CPUE in La Ni’a moved with the optimal parameter values of the fishing site in the thermocline. The factor of year had a fluctuating effect on the CPUE, and the influence of the La Ni’a year on the CPUE was closer. The areas with high abundance were 5°N—5°S, 150°E—175°E. From the above, the change of thermocline caused by abnormal climate had significant effect on CPUE.