Abstract:[Objective] To realize the unification of qualitative and quantitative evaluation, simplify the process of surface water environmental quality assessments, and reduce the public's difficulty in the cognition of water quality.[Methods] Using the surface water environmental quality index (SWQI), a statistical analysis was conducted based on 1.83×105 monitoring data points from the surface water monitoring network of Shaanxi Province from 2015 to 2019.[Results] Considering SWQIs, 78.7% of them were in the range of 2.5—8.0, which had the densest points. The number of samples in each interval of the SWQI index had an approximately normal or semi-normal distribution.[Conclusion] ① We used statistical methods to obtain the SWQI qualitative evaluation thresholds Ⅰ—Ⅵ (≤ 3.5, ≤ 5.0, ≤ 6.5, ≤ 8.0, ≤ 10.0, > 10.0). ② The verification showed that it was consistent with the current surface water environment quality evaluation method at three levels of verification (section, river, and region). The SWQI can be used to evaluate the surface water environmental quality and realize the transition to the current evaluation method.