Taking Tongren City in Guizhou Province as the research object, we establish an ecological security evaluation framework based on the PSR (Pressure-State-Response) model. Using system dynamics theory, we construct a simulation model of the ecological security system for Tongren City and conduct a comprehensive assessment of its ecological security from 2005 to 2020. This study aims to reveal the spatiotemporal evolution patterns and elucidate the influencing factors of ecological security in Tongren City. The research involves analyzing various indicators to understand the pressures, states, and responses within the ecological security framework. We incorporate data from multiple sources, including environmental, economic, and social parameters, to ensure a holistic evaluation. The assessment period from 2005 to 2020 provides insights into how ecological security has evolved over time and the factors that have contributed to these changes. Specifically, the analysis focuses on changes in land use, forest cover, water quality, and pollution levels.Our findings indicate that from 2005 to 2015, the average ecological security index in Tongren City increased by 14.34%, with 80% of the districts and counties showing an upward trend. This improvement can be attributed to enhanced environmental policies, increased investment in ecological protection measures, and improved public awareness and participation in environmental conservation efforts. However, from 2015 to 2020, the ecological security index decreased in all districts and counties except Wanshan District and Jiangkou County, with the average index dropping by 7.18%. This decline highlights emerging challenges such as rapid urbanization, industrialization pressures, and inadequate wastewater management, which have adversely impacted ecological security.The study identifies the added value of forestry and investment in environmental protection as the main factors positively influencing ecological security in Tongren City. Increased forestry activities have contributed to better air quality and biodiversity conservation, while substantial investments in environmental protection have helped mitigate pollution and restore degraded ecosystems. Conversely, urbanization level and wastewater discharge are the primary reasons for the decline in the ecological security index. High levels of urbanization lead to habitat loss, increased waste production, and higher pollution levels, while inadequate wastewater treatment exacerbates water pollution issues. These findings underscore the need for balanced development strategies that mitigate negative impacts on ecological systems and promote sustainable practices.To further understand future trends, we set up three scenarios: natural growth, sustainable development, and resource depletion, to simulate the spatiotemporal changes in ecological security from 2020 to 2035. The results show that under the sustainable development scenario, the ecological security of Tongren City improves, demonstrating the benefits of sustainable practices such as green infrastructure, renewable energy adoption, and comprehensive environmental regulations. In contrast, the resource depletion scenario leads to a decline in ecological security, highlighting the risks associated with unsustainable resource exploitation, deforestation, and over-extraction of water resources. This study suggests that implementing strategies such as tourism urbanization, balancing resource development and protection, and conducting ecological environment restoration can effectively address the challenges posed by different future development scenarios in this region. These measures are crucial for ensuring the long-term ecological security and sustainable development of Tongren City.