The invention belongs to the technical field of vulnerability attacks, and provides a vulnerability attack cost quantitative evaluation method based on a depth index, which comprises the following steps: generating a network model for a network to be attacked, and defining an attack graph model; generating a vulnerability attack graph by combining an attack graph generation algorithm according tothe network model and the attack graph model; in a vulnerability attack graph, analyzing an attack path from a starting node initiating an attack to a target node, and if the attack path is a multi-branch path, when the path depth between an attacker and a vulnerable node is obtained, considering the influence pe of an attack cost brought to the vulnerable node by an alternative path and a forcedpath, and calculating the attack cost of the vulnerable node; and finally calculating the cumulative attack cost to the target node. According to the method, the attack cost of the vulnerable points with the large depth in the attack path can be more accurately evaluated by combining the index of the depth of the attack path, and a better basis is provided for analyzing an actual attack process and an attack means.