The study was carried out to assess the quality, main influencing indicators and sources of impact on surface water quality of coastal provinces such as Soc Trang and Bac Lieu. Water quality data were collected at 19 sampling locations in Soc Trang province and eight sampling locations in Bac Lieu province in 2019 including parameters of temperature, pH, electrical conductivity (EC), turbidity (Turb), total suspended solids (TSS), dissolved oxygen (DO), chemical oxygen demand (COD), biological oxygen demand (BOD), ammonium (N-NH₄⁺), nitrite (N-NO₂^-) , nitrate (N-NO₃^-), soluble phosphorus (P-PO₄^3-), total Fe (Fe), total nitrogen (TN), total phosphorus (TP), sulfate (SO₄^2-), chloride (Cl^-), coliforms, total organic matter (TOC), alkalinity (Alk) and salinity (Sal). Principal component analysis (PCA) was used to identify the main factors affecting surface water quality in the study area. In Soc Trang, the results showed that the water quality shows signs of pollution by suspended solids, organic matters, nutrients and microorganisms in the central areas of the city, urban areas, inland areas and salinity. in coastal areas. The PCA results indicated that the parameters that need to be selected for monitoring included EC, TSS, COD, Cl^-, total Fe, SO₄^2- and BOD, N-NH₄⁺, P-PO₄^3-. In Bac Lieu, the results showed that the water quality is not suitable for domestic purposes. The parameters of TSS, COD, BOD, N-NO₂^-, N-NH₄⁺ and Cl^- all did not meet the permitted standards of QCVN 08:2015/BTNMT (column A2). The PCA results showed the criteria that need to be considered for monitoring such as pH, salinity, COD, BOD, TSS, total Fe, Cl^-, DO, N-NO₃^-, alkalinity and coliforms. The current results provide scientific information for monitoring water quality in the coastal provinces of the Mekong Delta.