Abstract: In order to investigate the distribution and content of alkanes in tobacco, the alkanes in tobacco were extracted respectively by Soxhlet extraction, ultrasonic extraction, simultaneous distillation extraction and steam distillation extraction. The extracts were concentrated and then purified by SPE-Si prior to GC/MS analysis. Ultrasonic extraction was finally chosen for the further study by balancing extraction time and the extraction yield of alkanes. The extraction parameters were optimized by single factor experiments and orthogonal experiment. The results showed that:1) The optimal parameters were:dichloromethane as solvent, ultrasonic power 560 W, extraction time 15 minutes, sample/solvent ratio 1:10, and repeated extraction for four times. The number of extraction repetition was the key factor affecting extraction yield. 2) Forty-one kinds of alkanes were identified by GC/MS analysis, among them, n-, i-, ai-alkanes between C₂₅-C₃₃ accounted for 99% of the total alkanes. This method is simple, fast and sensitive, features good reproducibility, and is suitable for the determination of alkanes in tobacco leaves.