Global warming has led to frequent droughts, which have become a serious threat to the sustainabledevelopment of social-ecological systems in the agro-pastoral ecotone. At the same time, the grassland ecological environment is deteriorating as a result of overloading and overgrazing, and the social-ecological systems in the agro-pastoral ecotone are under significant stress. In order to maintain the sustainable development of the social-ecological systems in the agro-pastoral ecotone, the State Council implemented the grassland grazing ban policy, the first round of grassland ecological subsidy policy, and the second round of grassland ecological subsidy policy in 2002, 2012, and 2016, respectively. However, since the implementation of the policy, the phenomenon of illegal grazing has existed for a long time, and the grassland ecosystem has been affected by illegal grazing by farmers, which has led to the failure of the forbidden grazing policy and the grassland ecological reward and subsidy policy to play an effective role, and the social-ecological systems in the agro-pastoral ecotone are still facing the risk of system collapse. Based on this, this paper takes Yanchi County of Ningxia, a serious area of grassland desertification, as an example, simulates the decision-making process of farmers' grazing behavior based on ABM(Agent-based model), and analyzes the influence mechanism of social norms, such as law enforcement and neighborhood effect, on the social-ecological system in the agro-pastoral ecotone under different drought levels.To demonstrate and simulate the actuality of the agro-pastoral ecotone, this paper combines the questionnaire research data, social-economic statistical data, part of the literature data, and grassland monitoring data of Yanchi County in 2021, sets the parameters in the ABM model, and constructs the social-ecological system model used to simulate the agro-pastoral ecotone under the disturbance of drought. The results show that (1) The income of farmers under the influence of drought shows a tendency of increasing and then decreasing, and the income of farmers is finally lower than the initial state. Meanwhile, the degradation trend of grassland ecosystem increased with the increase of drought probability. (2) Overall, when the grassland faces the impact of natural disasters such as drought, the increase in law enforcement has not been effective in ensuring the healthy development of the social-ecological system. Specifically, when drought comes with the increase of law enforcement efforts, the income of farmers can be maintained in a stable range, and the impact of law enforcement efforts on farmers' income is small. Moreover, the increase in enforcement efforts under different drought levels failed to effectively stop illegal grazing behavior, resulting in the continued degradation of grassland ecosystems. (3) The potent neighborhood effect can significantly influence the behavior and decision-making of farmers, and subsequently exert an impact on the social-ecological system in the agro-pastoral ecotone. When the behavioral decisions of farmers are profoundly affected by the surrounding farmers (that is, under the potent neighborhood effect), farmers are more prone to undertake illegal grazing, causing the influence of overgrazing and drought on the grassland ecosystem and leading to the deterioration of the grassland ecosystem. In the short term, illegal grazing leads to a notable reduction in farmers' production costs, thereby enhancing farmers' production efficiency and increasing farmers' income. However, in the long run, under the potent neighborhood effect, a large number of farmers engaging in illegal grazing results in the maximum livestock carrying capacity of the grassland ecosystem, the deterioration of the grassland ecosystem, farmers resorting to indoor feeding, the decline in the economic efficiency of farmers' production, and the gradual decrease in farmers' income.