The present invention relates to the crystalline forms of a 5-HT1F receptor agonist 2,4,6-trifluoro-N-[6-[(1-methyl-piperidine-4-yl)carbonyl]pyridin-2-yl]-benzene formamide (lasmiditan) and its hydrochloride. The crystalline forms of the present invention have advantages in crystallinity, hygroscopicity, morphology, crystal form stability, and chemical stability as compared with the known forms of lasmiditan and lasmiditan hydrochloride. The present invention also relates to processes for the preparation of the crystalline forms of lasmiditan and lasmiditan hydrochloride, pharmaceutical compositions thereof and their use in treating and/or preventing a patient's migraine and other diseases or conditions associated with 5-HT1F receptor dysfunction.