The study was conducted to assess the surface water quality on Xa No canal in Vi Thanh district, Hau Giang province. Surface water quality samples were collected at 3 locations with a frequency of 4 times per year including March, May, August and October 2020 from the Department of Natural Resources and Environment of Hau Giang province. The results showed that the temperature, pH and NO₃^--N in the study area are still within the allowable limits of QCVN 08-MT:2015/BTNMT, Column A1. Surface water in the study area was contaminated with organic (low DO, TSS, BOD, high COD), nutrients (NH₄⁺-N and PO₄^3--P exceeded permissible limits), heavy metals (Fe) and coliform. Water quality has obvious seasonal variation in which DO in August and TSS, BOD, COD, NO₂^--N in May were significantly higher than those in other months. NH₄⁺-N and PO₄^3--P in October were higher than those in March, May and August. Meanwhile, iron and coliform in March were significantly lower than those in other months. The results showed that the WQI (25 to 52) classified the water quality was from bad to moderate in which water quality in October was better than that in the other months. Surface water quality at Xa No canal was influenced by five potential polluting sources which caused 92.4% of water quality variation. All monitoring parameters (pH, temperature, TSS, DO, BOD, COD, NH₄⁺-N, NO₂^--N, NO₃^--N, PO₄^3--P, Fe and coliforms had impact on water quality and need to be continuously monitored. However, NO₂^--N, BOD can be considered to reduce because it can be predicted from other indicators such as DO, COD and NH₄⁺-N. Environmental management agencies need to find solutions to improve water quality, especially organic matters and microorganisms.