Based on the survey data of fishery resources and environment of four voyages from April 2021 to January 2022, the spatial and temporal distribution of Portunus trituberculatus and its relationship with influencing factors in the Ruian sea area were studied, including its marine dominance, community structure and resource density distribution. At the same time, generalized additive model (GAM) is used to analyze the relationship between resource density and influencing factors. The results showed that: in the Ruian sea area, P. trituberculatus is an important species (100 ≤ IRI < 1 000) in spring and summer and a dominant species (IRI ≥ 1 000) in autumn and winter. The average carapace length and body weight of P. trituberculatus ranged from 33.9 mm to 60.4 mm, and 22.9 g to 126.1 g. The carapace length and body weight of P. trituberculatus were the highest in summer and the lowest in autumn. There were significant differences between different seasons. P. trituberculatus showed negative allometric growth in spring, summer and winter (b < 3), and positive allometric growth in autumn (b > 3). The average resource density of P. trituberculatus ranged from 16.57 kg/km² to 422.60 kg/km², with the highest in autumn and the lowest in spring, and the average resource density in autumn was 25.5 times of that in spring. GAM analysis showed that the interpretation rate of the model was 80.2%. Season, surface water temperature, bottom water temperature, bottom salinity and surface chlorophyll a concentration had significant effects on the resource density of P. trituberculatus (p < 0.05), among which season had the greatest effect. Through this study, it provides reference for grasping the dynamic change law of P. trituberculatus resources in Ruian sea area, and further provides theoretical support for the proliferation and release of P. trituberculatus.