Abstract: Ecosystem service function is the basis for human survival and development. Scientific evaluation helps to intuitively understand the importance of ecosystems and promote ecological protection and ecological civilization construction. In order to quantitively evaluate the service function value of the public welfare forest ecosystem in Kaihua County and objectively reflect the effectiveness of its construction, this study took Kaihua County’s 2018 public welfare forest resources as the object and established a county-level monitoring system by setting up fixed sample plots. 13 indicators on public welfare forest water conservation, soil and fertilizer conservation, and carbon fixation and oxygen release were measured using distributed measurement methods following the Standard for the Evaluation of Forest Ecosystem Service Functions. The results showed: In 2018, the water conservation of public welfare forest was 2.338 2×10⁸ t, worth 2.464 billion yuan; the amount of soil consolidation and fertilizer retention were 2.804 2×10⁶ m³ and 1.350 0×10⁵ t respectively, worth 590 million yuan; carbon sequestration was 2.444 0×10⁵ t and oxygen release was 6.542 0×10⁵ t, worth 1.163 billion yuan; nutrient accumulation was 9 032.48 t, worth 116 million yuan; absorption of sulfur dioxide was 9 570.59 t and dust retention was 1.767 8×10⁶ t, worth 424 million yuan; the value of biodiversity conservation was 866 million yuan. The total biomass of the public welfare forests was 1.038 4×10⁷ t, and the biomass per hectare was 114.19 t. The biomass of Chinese fir forests was the largest, followed by broad-leaved forests, and shrubs had the smallest biomass. Chinese fir forests provided the highest value of ecosystem services, followed by broad-leaved forests and mixed coniferous and broad-leaved forests, the value of ecosystem services provided by shrubs was the least. In conclusion, the public welfare forests in Kaihua County have exerted great ecological benefits, but the potential has not been fully realized. With the optimization of stand structure and the improvement of research technology, the value of ecosystem services will be further increased. This study provided a case for evaluating ecosystem service functions, and further researches needed to be carried out.