Portunus trituberculatus is widely distributed in the coastal waters of China and is currently facing high fishing pressure. To protect and sustainably utilize the fishery resources of P. trituberculatus, this study was conducted based on survey data from an offshore trawl survey in Zhejiang Province in April (spring) and November (autumn) from 2020 to 2022. The spatial distribution characteristics and the relationship between Portunus trituberculatus and marine environment were analyzed using global autocorrelation analysis, hot spot analysis, and the geographical weighted regression (GWR) model. The results showed that the spatial autocorrelation in spring ranked from small to large in the order of 2020, 2022, and 2021, and that in autumn ranked from small to large in the order of 2022, 2021, and 2020. In 2021 and 2022, the spatial aggregation degree of P. trituberculatus in spring was higher than that in autumn, whereas that in 2020 was lower than that in autumn. The local autocorrelation showed that the distribution of hot spots in spring and autumn was regular. In spring, P. trituberculatus mainly concentrated around the waters near the northwest of the Zhoushan Sea area at coordinates 121.7°–122.5° E, 30.7°–31° N, whereas in autumn, it concentrated around the northeastern part of the Zhoushan Sea area at coordinates 122.5°–123.25° E, 30°–31° N. The GWR model showed that environmental factors had spatial non-stationary effects on resource distribution of P. trituberculatus during different seasons. The spatial heterogeneity degree of environmental factors on resource distribution of P. trituberculatus spring was in the order of bottom sea dissolved oxygen (SBD)＞bottom sea temperature (SBT)＞bottom sea salinity (SBS). The spatial heterogeneity in autumn was in the order of SBT＞SBD＞SBS. This study contributes to understanding the spatial distribution of P. trituberculatus in offshore waters of Zhejiang, thereby providing a scientific foundation for the management of fishery resources.