Abstract: Graph and complex network theory were used to construct the network topology of long-distance water delivery system. Node attack was selected due to its higher destruction efficiency. Under the condition of having unknown, partially known and fully known about the network topology, the attack strategies of random attack, conditional attack and deliberate attack were implemented respectively, and then the invulnerability of the water delivery system under different attack strategies was evaluated. The degree, betweenness and closeness centrality were furtherly used to quantify the node importance under the condition of having fully known about network topology, then the response of water delivery system invulnerability to different node importance indexes was analyzed. The results show that deliberate attack is the most efficient while the random attack has the lowest efficiency, and as information acquisition increases, the attack efficiency increases correspondingly. Node betweenness has the greatest impact on water delivery system invulnerability while node degree has the least impact. This study can provide theoretical support for the identification and protection of important facilities in long-distance water delivery systems.