In order to make a scientific reasonable plan for the total amount control of water pollutants, taking Zhangjiagang City as an example, a single-factor environmental Gini coefficient model was constructed, which involved in the factors of population, resources, economy and water environment tolerance. The main unfair pollutant distribution units were also analyzed by selecting the contribution coefficient as a judge. According to the minimum model of Entropy-Environmental Gini coefficient, the total amount allocation of ammonia nitrogen based on multivariate fairness in the towns of Zhangjiagang was proposed. The research found that there is no consistency between the proportion of pollutant reduction and the current discharge of pollutants in the total water pollutant load allocation process, and the final allocation scheme should be determined by considering many factors. In this study, the minimum model of entropy-environmental Gini coefficient takes many objective factors such as society, economy and resources into account. As for the plain river network areas, due to its special geographical location and natural conditions, the distribution of population and resources is relatively uniform, so the allocation scheme based on the model fully embodies the principle of multivariate fairness, which is more fair and reasonable.