The present invention belongs to the field of pharmaceutical chemistry, anddisclosedare two crystal forms of Chidamide, that is, Chidamide crystal form A andChidamidecrystal form B, and the method for preparing the new crystal forms ofChidamide. TheChidamide crystal form A and Chidamide crystal form B of the present inventioncanbe used for preparing drugs for treating diseases related to celldifferentiation andproliferation.