Speed and accuracy must both be taken into consideration when using Terahertz TimeDomain Spectroscopy(THz-TDS) for security inspection of flammable and explosive contraband liquids in railway transportation. Due to speed limitation, the exact comparison of the precise fingerprint location between testing results and database, which is the common method adopted in laboratory analysis, cannot be directly utilized for the security inspection of large passenger flow. The reflective terahertz time-domain spectroscopy data for typical liquids in railway transportation is acquired under standard temperature, pressure, and normal humidity level(25 ℃ , RH 60%). The categorized timedomaindatabase for non-flammable and non-explosive liquids, flammable and explosive liquids, and strong acid, is established. Based on the database, the typical time-domain pulse patterns can be classified into four categories, namely terahertz time domain spectroscopy with obvious secondary pulse, minor secondary pulse, no secondary pulse and obvious negative secondary pulse. According to terahertz time domain characteristics, rapid detection with better than 80% of accuracy is achieved through classification decision model.