Abstract: In recent years, network vulnerability analysis, which is attracting more and more domestic researchers and foreign researchers, has become a hotspot in the field of information security. A new model of network security analysis based on the increase in attack ability is proposed. It takes into account the network environment and simulates the attacker's behavior, and considers improving the attack ability as attacker's ultimate target to generate attack graph. The method used to represent attack graph make the attack target more clear, because it uses the attack ability's increment to describe a goal, which is more accurate than the attack ability itself. The minimum attack cost analysis considers the influence of similar attacks to compute the cost of each path for the first time, which conforms to the actual process of attack execution. The minimum environment change analysis can help people find out which attack path is most likely to be adopted by the attacker, which deals with IDS in a more reasonable way. These two analysis methods are helpful for improving the network configuration. The algorithm of attack graph generation and the method to analyze the attack graph proposed by the network security analysis model is more feasible than the existing ones.