Dongzhai Harbor Mangrove forest, which is one of the largest mangrove forests in China, is currently contaminated by antibiotics from aquaculture and human activities in the vicinity. However, insufficient research has been conducted on antibiotic pollution in Dongzhai Harbor, which could affect the antibiotic pollution levels in the mangrove forest. In this study, the occurrence, distribution and risk assessment of 37 antibiotics in the seawater and sediment of Dongzhai Harbor were analyzed. Thirty-one and 27 kinds of antibiotics were detected in the seawater and sediment of Dongzhai Harbor, respectively. The average concentrations of total antibiotics in the seawater and sediment were 62.81 ng/L and 2.26 ng/g dw, respectively, which were at a low to moderate pollution levels. Ciprofloxacin (CFX) (11.44 ng/L) and oxolinic acid (OA) (5.33 ng/L) were the main antibiotics in seawater. CFX (1.77 ng/g dw), enoxacin (ENX) (1.64 ng/g dw), cinoxacin (CINX) (1.09 ng/g dw) and norfloxacin (NFX) (1.03 ng/g dw) were the main antibiotics in the sediments. Correlation analysis revealed that the sediment-water partition coefficient (Kd) values of the 13 antibiotics were significantly positively correlated with the molecular weight (MW), octanol water partition coefficient (Kow) and LogKow of the antibiotics. The results of multiple linear regression analysis revealed that the Kd of ofloxacin (OFX) was significantly positively correlated with the organic carbon content (foc) in the sediments. The results of the principal component analysis and positive matrix factorization (PMF) receptor model revealed that the antibiotics in Dongzhai Harbor were derived mainly from aquaculture wastewater, domestic sewage and livestock and poultry breeding operations in the vicinity of Dongzhai Harbor. OFX in seawater posed a low risk (0.00-0.29) at 91 % of the sampling sites, whereas ENX (0.22), CFX (0.07), enrofloxacin (0.24), OFX (0.36) and NFX (0.10) in sediments posed a medium-high risk at more than 70 % of the sampling sites. The antibiotic mixtures (0.08-3.61) in the sediment posed moderate and high ecological risks at 50 % and 45 % of the sampling sites, respectively. To assist regulators in monitoring and managing antibiotic pollution in Dongzhai Harbor, sulfadiazine (SDZ) and OFX were selected as indicators of antibiotic pollution in the seawater of Dongzhai Harbor. The results of the present study provide a theoretical basis for managing and preventing antibiotic pollution in gulf and mangrove ecosystems in Dongzhai Harbor.