The zooplankton specimens were investigated in Pacific saury (Cololabis saira) fishing grounds of northwestern Pacific Ocean from July to September in 2005, and then were analyzed by species, amount and distributions. The results showed that 25 genera of zooplanktons were identified, which belonged to Crustacea, Sagittoidea, Amphipoda, and Euphausiacea were the highest. The biomass of zooplanktons distribution was not even, with peak zones around the sites closed to EEZ of Russia and the sites north to 46°30′N. The average site-biomass was (430.06±251.18) mg·m^-3, with 11 sites more than 500 mg·m^-3. Gray correlation theory and stomach content method were used to build the relationship between the distributions of zooplanktons and Pacific saury. The average daily saury catch was (7.72±5.25) t·d^-1, average daily catch per net was (0.78±0.33) t·net^-1, according to Gray correlation theory, both of them had a comparatively high relation coefficient with the distributions of Copepoda, Chaetognatha, and Amphipoda. And with the analysis of contents from Pacific saury specimens’s stomachs, the most frequently detected zooplankton was Copepoda, followed by Chaetognath, Mysidacea, Amphipoda and Tomopteridae. In all zooplanktons, the site-occurrence-rates of Copepoda and Chaetognatha were the highest, 100% and 93.3%, and the average biomass of which were 298.56 mg·m^-3 and 118.09 mg·m^-3 and the summation accounted for 96.88% of total biomass. The result shows that these two species created a strong relationship with the distribution of saury fishing grounds, and their biomass can be considered as the important indicator of looking for the main saury fishing grounds.