To evaluate the river chief system implementation effect, we selected 15 evaluation indexes from five aspects, namely the effects of water conservation, the effects of water pollution prevention and control, the effect of water environment improvement, the effect of people’s livelihood and the effect of law enforcement and supervision. According to the obtained evaluation standard, we built up an evaluation model for the implementation of river chief system based on the combined weight-ideal interval method. With this model, the analytic hierarchy process (AHP) method and objective weight method were used to obtain the combined weight, and ideal interval method was used to evaluate the implementation effect of the river chief system. This model was then used to evaluate the river chief system implementation effect of Shaanxi Province in 2012-2018. Through the adoption of combined weight which took advantage of both subjective and objective weights, more stable, reasonable and accurate results were obtained. The results showed that the implementation effect of Shaanxi Province improved year by year, and it reached excellent level in 2017, which was consistent with the actual situation. The implementation effect of the river chief system was further optimized in 2018. It is proved that this model has universal applicability for the evaluation of the implementation effect of the river chief system.