Statistical methods were combined with mathematical modelling to analyze the causes of the abnormal changes in dissolved oxygen concentration, and the effects of restoration measures on dissolved oxygen anomalies in water environment. Taking the Yanhe River in Jiangsu Province as the case study, we analyzed dissolved oxygen concentration, related water quality factors, and rainfall data using Pearson correlation analysis, so as to identify the main influencing factors. Then, the corresponding MIKE11-Ecolab coupled model was established to compare the effects of different restoration measures on the dissolved oxygen concentration of the river network. The results showed that dissolved oxygen concentration was significantly and negatively correlated with water temperature, rainfall, permanganate index, and biochemical oxygen demand. Water temperature, stormwater runoff pollution, and photosynthetic efficiency had the greatest impact on dissolved oxygen. With an increase of 20% in water temperature, dissolved oxygen concentration decreased by 53.68%; a reduction of 50% in stormwater runoff pollution led to an improvement of 26.48% in dissolved oxygen concentration; an increase of 50% in photosynthetic efficiency improved the dissolved oxygen concentration by 16.43%. This study can provide a reference and theoretical basis for water ecological restoration in river network areas.