Abstract: Fishery stock surveys were carried out in May, August and November 2016 and February 2017, and spatiotemporal dynamic of the crustacean community structure and its relationship with the environmental factors of the Fangchenggang Bay were analyzed. A total of 60 crustacean species in 2 orders, 19 families and 35 genera were collected, among which the warmwater species and warmtemperate species accounted for 60.0% and 40.0%, respectively. The species numbers recorded were 51 in spring, 34 in summer, 35 in autumn and 26 in winter. The similarity index was the highest in autumn and winter. The dominant species defined by the index of relative importance (IRI) higher than 500 were composed of Parapenaeopsis hungerfordi, Charybdis hellerii, Marsupenaeus japonicus, Metapenaeus ensis and Metapenaeus affinis, and the main species with IRIs ranging from 100 to 500 were Metapenaeopsis barbata, Fenneropenaeus penicillatus, M. intermedius, Oratosquilla oratoria, M. joyneri andPortunus pelagicus. The most dominant species is P. hungerfordi in spring, M. ensis in summer, M. affinis in autumn andC. hellerii in winter. The annual average density and biomass in the bay were 32 201 ind./km² and 212.29 kg/km² , respectively. Seasonal and spatial variations of density and biomass were significant. Species number (SN) ranged from 2 to 17 with species diversity index (H′) from 0.200 to 3.160, richness index (d) from 0.200 to 2.230 and evenness index (J) from 0.160 to 0.988. Spacious variations were significant for SN, H′, d and J , but seasonal variations, only for SN and J. The analysis of clustering, similarity (ANOSIM) and similarity of percentage (SIMPER) showed that spatiotemporal heterogeneity existed in the community structures to some extent. Biota and environment matching (BIOENV) showed that the major environmental factors determined the seasonal distribution patterns of the crustacean communities in the bay.