In order to investigate the distribution of the yellowfin tuna (Thunnus albacares) in the fishing grounds in the tropical Atlantic Ocean, the isothermal distribution of subsurface temperatures in the yellowfin tuna fishing grounds was evaluated. The depths of 13℃ and 8℃ isotherm from the sea surface temperature (SST) (Delta 8℃), were plotted on spatial overlay maps using data collected on a monthly basis from Argo buoys and monthly CPUE data (catch per unit effort) from Thunnus albacares long-lines supplied by the International Commission for the Conservation of Atlantic Tunas (ICCAT). In addition, the differences in depth between the 13℃ and delta 8℃ isolines at the lower boundary of the thermocline were computed to determine the relationship between Thunnus albacares vertical distribution and thermocline depth. The overlay maps suggest that the delta 8℃ isothermal depth distribution showed obvious seasonal variation, roughly in the zonal striped distribution on the annual mode. The spatial distribution of the delta 8℃ isothermal depth is deep in winter and shallow in summer. The delta 8℃ isothermal depth is shallow, lying at 150 m in the low latitude area throughout the year. The topography of the 13℃ isothermal depth showed little seasonal variation. The 13℃ isothermal depth was greater than 250 m to the north of the slope, which started 15°N of West Africa and ended 10°N of South America, and to the south of the slope, which started from 10°S of South America and ended 30°S of West Africa. In the triangular area between these two slopes, the 13℃ isothermal depth distribution ranged from 150 m to 200 m. The CPUE is highest in areas where the 13℃ isothermal depth was shallower than 250 m (mode: 170-249 m). Conversely, if the depth is greater than 250 m, the CPUE tends to be low. Similarly, the highest CPUEs were observed in areas where the delta 8℃ isothermal depth was shallower than 150 m (mode: 50-139 m) in the latitude area between 5°S and 10°N throughout the year, whereas the delta 8℃ isothermal depth reached 150-350 m offshore of the west coast of Africa in the southern hemisphere from July to October. The vertical distribution of high hook rates was concentrated in the area between 5°S and 10°N. The horizontal distribution of Thunnus albacares in the tropical Atlantic Ocean was affected by the 13℃ isothermal depth, and the vertical distribution of Thunnus albacares was affected by the low boundary temperature and depth of the thermocline. Frequency analysis and the empirical cumulative distribution function were used to compute the optimum range of subsurface factors. The optimum ranges for 13℃ and delta 8℃ isothermal depths were 180-240 m and 50-139 m, respectively. The optimum depth difference ranges were 70-29 m for 13℃ isothermal depths and 30-149 m for delta 8℃ isothermal depths. The results were confirmed by using the Kolmogorov-Smirnov test. The distribution interval and vertical depth range for the central fishing ground of Thunnus albacares was documented, and the results provide a reference for improving the efficiency of long-line fleet and resource management.