The study was conducted to assess the quality of surface water in the aquaculture area of Kien Giang province in the period of 2019-2020. Water samples were collected twice per year (in March and September) at seven locations designated AQ1 to AQ7. The parameters of temperature (T), pH, salinity (S), total suspended solids (TSS), dissolved oxygen (DO), chemical oxygen demand (COD), ammonium (N-NH₄⁺), orthophosphate (P-PO₄^3-), Coliform, iron (Fe), and silicon dioxide (SiO₂) were used to assess water quality. The study used national regulation on marine water quality (QCVN 10-MT:2015/BTNMT) and multivariate statistical methods including cluster analysis (CA) and principal component analysis (PCA) to assess water quality. The results showed that the temperature and pH are within the allowable limits. Salinity, COD, and SiO₂ are in the ranges of 7.7-22.2‰, 18.3-22.8 mg/L, and 8-16.3 mg/L, respectively. These criteria are not specified in QCVN 10-MT:2015/BTNMT. TSS at positions AQ5-QW7 exceeded the allowable limit. DO at all positions in May 2019 and all sampling periods of 2020 were below the allowable limit. N-NH₄⁺ appeared at all sampling locations in March 2019 while N-NH₄⁺ appeared at only a few locations in September 2019 and also in 2020. In the locations where N-NH₄⁺ was found, N-NH₄⁺ were all over the allowable limit. P-PO₄^3- was found only at AQ1 (2019) and AQ4-AQ6 (2020) positions. Coliform at AQ3, AQ6, AQ7 exceeded the allowable limit of QCVN 10-MT:2015/BTNMT. Fe at all positions has exceeded the allowable limit. The large fluctuations in time and space of surface water quality was mainly due to COD, TSS, salinity, N-NH₄⁺, coliform, Fe, SiO₂. The results of PCA analysis showed that the parameters of pH, salinity, TSS, COD, N-NH₄⁺, P-PO₄^3-, Fe, SiO₂, coliform need to be continued to be monitored because they have the main impact on surface water quality. Further studies need to investigate specific sources of pollution in order to have appropriate treatment solutions.