Abstract: With the surge in demand for lithium-ion batteries in various fields, concerns about their safety have increased. Electrolyte leakage, as a critical safety hazard, often goes unnoticed due to its subtle occurrence and the volatility of electrolyte components. In the application of on-site analysis, gas sensors are limited by their sensitivity and qualitative capability. Traditional gas chromatography-mass spectrometry (GC-MS) is not suitable for on-site analysis due to its size and inconvenient operation. Portable chromatography-mass spectrometer has the advantages of high efficiency, small size, light weight, and low power consumption, and is suitable for on-site determination of volatile organic compounds (VOCs). In this study, a vacuum-assisted volatilization system was developed, and a rapid on-site analytical method for microleakage of lithium battery electrolyte was established based on adsorption/thermal desorption-portable gas chromatography-mass spectrometry (ATD-GC-MS). Under the experimental conditions of a sampling volume of 300 mL, a split ratio of 50:1 and a thermal desorption temperature of 180 ℃, the limit of detection and limit of quantification for electrolyte-dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are 1.57-2.27 μg/m³ and 4.99-7.23 μg/m³, respectively. The results show a good linearity in the concentration range of 7.85-5270 μg/m³ and 5078-89167 μg/m³ with the coefficient (R²) greater than 0.997, and the recovery of standard addition is between 84.21% and 103.21%. When the pressure in the vacuum-assisted volatilization system is set to −27 kPa, the duration of a single detection is less than 8 min. To further verify the practicality of the method, a microleakage simulation system was developed and used in microleakage detection experiments on two types of 18650 and 21700 cylindrical lithium batteries. The results demonstrated that the detection method possesses the capacity to swiftly and accurately detect microleakage in lithium batteries. The method has the advantages of simple operation, high efficiency and high accuracy, positioning it as a suitable solution for on-site rapid detection of microleakage of lithium batteries and offering a significant advancement in battery safety assessment and quality control.