To study the spatio-temporal distribution and seasonal variation of resource density of Oratosquilla oratoria in Hangzhou Bay and its adjacent waters, single bottom trawl surveys and environmental data collection were conducted in March (winter), May (spring), July (summer), and November (autumn) in 2014. The spatial distribution characteristics of resource density, seasonal variation of barycenter, and body mass were analyzed, and the relationship between resource distribution and environmental factors was analyzed using GAM model. The results showed that the average resource density of Oratosquilla oratoria in Hangzhou Bay and its adjacent waters showed a changing trend of autumn＞winter＞spring＞summer, with the average resource density of 20.40 kg/km² in autumn being the highest, and 10.09 kg/km² in summer being the lowest, which was more than twice that of summer. The Oratosquilla oratoria resources were mainly distributed on the offshore side of the island chain formed by Zhoushan island-Qushan island-Sijiaoshan-Huaniao Mountain, while the distribution of the Oratosquilla oratoria was relatively small on the coastal side near the mouth of Hangzhou Bay. The center of gravity of its resource density was located at a water depth of 30–40 m, and the overall trend was from south to north, from outside to inside. The average body mass of Oratosquilla oratoria individuals showed the order of summer＞winter＞spring＞autumn, and no significant difference was observed in body mass between different seasons. GAM model analysis showed that season, bottom salinity, and bottom chlorophyll significantly affected the resource density of Oratosquilla oratoria. The bottom salinity was the most significant factor affecting the distribution of Oratosquilla oratoria, and the average bottom salinity of Oratosquilla oratoria occurence showed the trend of summer＞winter＞spring＞autumn. This study provides technical support for revealing the spatio-temporal distribution and seasonal variation of the resource density of Oratosquilla oratoria in Hangzhou Bay and its adjacent waters. It also provides guidance for effectively managing and rationally utilizing Oratosquilla oratoria resources in this area.