The characteristic fingerprint spectrum of levodopa (L-DOPA) in the frequency range of 0.5-14.5 THz was obtained by using an air plasma terahertz time-domain spectroscopy system, and the variation in absorption spectrum with temperature was investigated. Density functional theory was used to calculate the L-DOPA crystal cell structure and for the spectral analysis of terahertz vibration. The results show that L-DOPA terahertz absorption peaks correspond to different collective vibrations and molecular local vibrations. The collective vibrations of L-DOPA have a wide distribution in the terahertz range, and the benzene ring and molecular side chain exhibit distinct vibrational modes. The vibration specificity is closely related to the molecular conformation and hydrogen-bonding interactions.