The urban river network in the plain area has various water environment problems such as poor water replenishment effect and deterioration of water quality. In order to solve these problems, we adopted the approach of problem analysis and method optimization to carry out the research on water replenishment scheduling strategies for water quality improvement of urban river networks. The approach included three parts: analyzing and evaluating the present situation, validating the strategies, and proposing implementation schemes. A case study of Tianjin City was carried out. Based on analysis of the current problem, we uncovered the reasons for the substandard water quality of the river network and put forward a set of water replenishment scheduling strategies. Based on the recommended strategies, we proposed an annual overall implementation scheme and an actual implementation scheme. The water demand of the annual overall implementation scheme was 319 million cubic meters. This study showed that the proposed research approach for water replenishment scheduling strategy could increase water utilization efficiency and improve water quality effectively. The approach can be applied to other river networks in plain areas.