A trip of productionpossibility frontier on exploring purple flying squid （Sthenoteuthis oualaniensis） has been made by Chinese squid jigging fleet in the northwestern Indian Ocean during September and November in 2003. It aimed to estimate the resources biomass of squid and its distribution. During the investigation period, the main fishing ground was found in the waters near 16°N, 61°E , where the averaged catch per day was more than 5 tons. But the fishing ground disappeared suddenly 10 days later. The situation of fishing ground changing and disappearing have been discussed based on the marine environmental data from the trip and satellite data from website. The upwelling might occur in the area along the coast of Oman. The upwelling might bring the oxygenpoor seawater from deeper layer, which might result that fish gather in pockets of relative oxygenrich water, at the same time fish tend to gather around areas where there is ample food, areas where there is high sea surface chlorophyll-α(Chl-a)) and lower sea surface temperature (SST). The fishing ground had been found at the area with high SST and Chl-a gradient. From the surface winds direction and speed data, it is showed that the appearance of lower cyclone will change the SST and Chla distribution, and plays a very important role in the forming of squid fishing ground.