Jumbo flying squid (Dosidicus gigas) distributed in the southeastern Pacific is not only an important economic oceanic squid, but also one of the important fishing targets for Chinese jigging fleets. The researches on distribution of this squid and its relationship with environmental conditions such as water temperature and its structure are the key content in searching for the mechanism of fishing ground and inherent laws. In this study, based on the fishing data from Chinese squid jigging fleets in the waters off Peru from January to December 2006, and the environmental data including sea surface temperature (SST), the water temperatures between 5 and 180 m, and the horizontal gradient of temperature (D) calculated by three different methods (D_max, D_square and D_mean), the spatial plots of CPUE, SST, D and the vertical temperature structure are drawn respectively by use of software ArcGIS 9.0 and Sufer 8.0 to analyze the distribution of fishing ground and its relationship with structure of sea water temperature. The result indicated that the main fishing ground was around 80-85°W and 10-17°S with the range of 18-28℃ SST, and the spatial variations in the catch distribution were evident. From June to August, the monthly catch was relativly high in the waters of 81-83°W and 12-13°S with the range of 18-23 ℃. The distribution of fishing ground was closely related to the D, the indicator D_square (P<0.001) was better than the two others, and the range of D_square was 0.6-1.7 ℃ in the main fishing ground. The results also showed that the upwelling was centralized around 12-13°S and 81°W during June to August, and the fishing ground was mainly distributed at the edge of upwelling between 81°30′-82°30′W. Therefore, it could be concluded that the fishing ground was formed by the upwelling, which was distributed at the mixed region between oceanic warm water and cool water caused by upwelling, and was closely related with the optimum SST, D and vertical temperature structure.