The connectivity of the river and lake system is a new concept of water treatment proposed in the new era. According to the concept, the rivers and lakes can be connected by constructing new canals and channels, also by the transformation of lakes, by which differnt rivers and lakes become an interconnected water network system. Based on the complex network method, the connectivity of the water network of the Haihe River Basin was analyzed from the two levels of the node and the subbasin. At the subbasin level, the connectivity of the basin was evaluated by the average index, and the overall water system connectivity of the basin was analyzed using the network diameter, average path length, etc. as supplementary indicators. At the level of a single node, the connectivity of each node in the basin was analyzed using degree index and betweeness centrality index. Therefore, the water system connectivity was analyzed from both node and subbasin levels, which realized the combination of microscopic and macroscopic perspectives. In addition, the clustering coefficent was also introduced for a better understanding of the spatial distribution characteristics of the river network in each subbasin. According to the rationality assessment of the results, it can be seen that the complex network method is conducive to the analysis of the characteristics and connectivity of the water system in the basin, and this method has excellent application prospects.