Rising geopolitical tensions present significant risks to national energy security, coinciding with a critical moment in the global energy transition. Securing stable energy availability has thus grown increasingly vital for pursuing nations’ climate targets. Deep decarbonization of the energy system remains a cornerstone of China’s long-term modernization agenda but is hindered by challenges like mitigating oil supply risks. External oil supply of China is exposed to high risk due to potential interruption in global chokepoints such as Strait of Hormuz and Strait of Malacca. This study therefore investigates how the ongoing energy transition will reshape China’s long-term oil security landscape and its short-term resilience to such supply disruptions. In this study, we employed our self-developed integrated assessment model (IAM), called IAMET, to quantify future energy development pathways and evaluate China’s oil security by integrating IAM with a forward-looking assessment framework. System reliance is used to simulate oil security under oil supply disruptions and the enhancement space of resilience are estimated. Results indicate that: ① By 2060, China’s oil demand will be around 200-300 million tons under carbon neutrality constraint, reducing the country’s oil import dependency ratio from the current 72% to 41%-60%, while oil security will face acute risks in the next 10-15 years. ② Energy transition will help to enhance oil supply resilience. Under a simulated disruption of 39%-66% of overseas oil imports, oil supply resilience will be “moderate” under carbon neutrality scenario. ③ Strategic petroleum reserves and demand rationing policies have different temporal effects on oil supply resilience enhancement. By adjusting energy demand structure, resilience will rise sharply in the early phase with greater possibility to belong to “good” zone, while current oil strategic stock has larger effects in the later phase as the oil demand shrink. This study underscores the growing role of IAM in evaluating oil security and emphasizes that reducing oil consumption through demand-side strategies can effectively complement supply-side actions to safeguard national energy security.