[Objective] The surface water quality after the comprehensive treatment of tailless manganese ore at the mud field in Guzhang County in Hu'nan Province was studied in order to provide the basis for the pollution control of heavy metals in the study area.[Methods] The pH value, Mn, Pb, Hg, As, Cu, Cd, Cr⁶⁺, chemical oxygen demand (COD) and NH₄⁺-N in the samples were determined. The water environment quality was evaluated by comprehensive pollution assessment and health risk assessment methods.[Results] ① The Mn content from sampling points S₃(upstream of culvert exit), S₄(downstream of Hengyuan Mining) and S₅(end of mud fiold river) exceeded the class Ⅲ standard of the Environmental Quality Standard for Surface Water (GB 3838-2002). ②As effected by the discharged wastewater from Zhang's manganese industry, the comprehensive pollution index of water environment ranged as S₃(upstream of culvert exit) > S₄(downstream of Hengyuan Mining) > S₅(end of mud fiold river) > S₁(upstream of manganese slag reservoir) > S₂(culvert exit). ③The results of health risk assessment showed that the total health risks (RT) of the S₁ to S₅ sampling point were 7.73×10^-6, 1.19×10^-5, 4.23×10^-5, 2.64×10^-5, 2.40×10^-5, respectively, all of which not exceeded the maximum acceptable risk level of International Commission on Radiological Protection(5.0×10^-5).[Conclusion] The total health risk of water environment is mainly derived from non-carcinogenic substances. Reducing Pb and Cu in the water environment can effectively control the total health risks caused by drinking water. Overall, the implementation of the comprehensive management of the tailing-free manganese mine at mud field in Guzhang County has achieved the target, and the water environment quality has basically reached the standard.