Stout camphor essential oil has a special scent due to its content of specific aromatic terpenoid compounds. Essential oils prepared from different species, varieties or subspecies have been shown to possess varied compounds. Of the major essential oil components extracted from the Stout Camphor tree, α-terpineol has been shown to be a key component, while essential oils prepared from other camphor species may not contain this terpene alcohol. Therefore, α-terpineol can be used as an index element to represent the purity of Stout Camphor essential oil. However, a method that can quantitatively examine the quality and purity of commercial Stout Camphor essential oils is necessary. By adding an internal standard to essential oil samples, this study aimed to develop a simple and reliable method for determining the level of α-terpineol in Stout Camphor essential oils on the market. Capillary column gas chromatography has the advantages of high resolution and high sensitivity, and is still one of the most important spectral analysis techniques in modern times. Therefore, this study developed a rapid method that used vanillin as an internal standard to determine the level of α-terpineol, a key component of the essential oil extracted from the stout camphor tree, using gas chromatography. The analysis of each sample only required 30 min. The lowest limit of quantitation was as low as 1 μg·mL-1. Add α-terpineol 1.0 and 10.0 mg to commercially available Cinnamomum micranthum Hayata essential oil and stout camphor wood essential oil, and the recovery rates were more than 98% (98%~103%) with a coefficient of variation below 10.8%. We then analyzed 15 commercially-available essential oil samples and one essential oil sample directly extracted from stout camphor wood. We found that the levels of α-terpineol in these samples were within the range of 21.3%～51.6%. In conclusion, this method has a high accuracy, and the α-terpineol levels can be used as an index to rapidly determine the quality of the stout camphor essential oil on the market.