The study was conducted to assess surface water quality and identify the main parameters influencing the surface water in Kien Giang province, study took the monitoring data at 49locations in 2019.  Water quality variables were pH, temperature, conductivity (EC), salinity, total suspended solids (TSS), dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), orthophosphate (PO₄³-P^-), ammonium (NH₄⁺-N), nitrate (NO₃^--N), nitrite (NO₂^--N), total iron (Fe), chloride (Cl^-) and coliform. Surface water quality was assessed using QCVN 08-MT:2015/BTNMT and water quality index (WQI). Principal component analysis (PCA) was used to determine main water quality parameters influencing on water quality. The findings presented that water environment in Kien Giang province was polluted by organic matters (DO was low; TSS, COD, BOD were high), nutrients (PO₄^3--P, NH₄⁺-N, NO₃^--N, NO₂^--N), microorganism (coliform) and Fe. WQI values indicated that water quality in the rainy season was worse than that in the dry season, mainly from poor to moderate. The PCA results showed that EC, salinity, Fe, Cl^-, BOD, COD, NO₃^--N, PO₄^3--N and coliform significantly influenced on surface water quality. Therefore, these water variables should be included in the annual monitoring program in Kien Giang province. The main sources of surface water pollution could be from agriculture drainage, dead aquaculture, domestic activities, untreated pollutant/waste water from industry, river bank erosion and hydrological factors. However, in order to properly manage the surface water quality, the sources of pollution need to be soon identified.