To meet flood control demand, many reservoirs have been built successively in China for many years. Reservoir inflow synchronization analysis for multiple reservoirs in the flood season can provide a reference for the formulation of the joint water supply operation plan and improve the utilization efficiency of water resources. In this paper, a two-dimensional copula model is used to analyze the reservoir inflow synchronization between a single reservoir on a tributary and the reservoir on the mainstream of the river in the flood season. Based on the obtained results, a R-vine copula model is established by selecting a suitable structure to analyze the multidimensional joint reservoir inflow synchronization for multiple reservoirs in the middle and lower reaches of the Yellow River basin in the flood season. For four selected reservoirs in the middle and lower reaches of the Yellow River basin in China as a case study, the frequencies of synchronous wetness and synchronous dryness for the four reservoirs are 15.106% and 15.209%, respectively. The research results can serve as a reference for actual scheduling.