The water resources in Northwest of Shandong Province is relatively poor and heavily depends on the Yellow River. But when the runoff of Yellow River is very small and rainfall in Southeast of Shandong Province is relatively abundant, the abundant water resources of Linyi city in southeast Shandong could be used for supplying the Northwest of Shandong Province. The Copula functions were applied to study the 2-dimensional wetness-dryness encountering probabilities between the precipitation of Yellow River and Linyi, and of Dezhou and Linyi. Their feasibility of wetness-dryness complementarity were analyzed . A comparison between the results using the Copula functions and Statistical method were conducted. The results showed that, the conclusion was reasonable, it had a great significance in optimally utilizing water resources and provided a technical support for making the united regulation and decision between Shandong Province and the Yellow River.