This study evaluates the quality and identify key variables influence on surface water quality in Soc Trang province, Vietnam. Water parameters of total suspended solids (TSS), dissolved oxygen (DO), biological oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC), nitrite (N-NO2-), nitrate (N-NO3-), ammonium (N-NH4+), orthophosphate (PO43--P), total nitrogen (TN) and total phosphorus (TP), turbidity (turb), pH; temperature (T), sulfate (SO42-), electrical conductivity (EC), chloride (Cl-), coliform, and iron (Fe) were used for the assessment. The findings revealed that most of the water parameters of TSS, DO, BOD, COD, TOC, N-NH4+, N-NO2-, Cl-, Fe, and coliforms exceeded the limits of QCVN 08-MT:2015/BTNMT, column A2, B1. The water quality in Hau River was better than the other locations. Saline intrusion has become the concern for surface quality in the study area. PCA showed that five PCs explained 87.9% of the variation of surface water quality in the study area and the parameters including BOD, N-NH4+, TN, TOC, Cl-, TSS, SO42-, Fe and coliforms were the main variables influencing surface water quality in the study area. Potential sources of water pollution are saline intrusion, hydrological regime, runoff, agriculture, industry, and domestic activities.