The present disclosure discloses a crystal form of a casein kinase 1ε inhibitor and a preparation method and use of the crystal form. Specifically, the present disclosure relates to a crystal form of the compound ( S )-2-(1-(4-amino-3-(2,3-difluoro-4-methoxyphenyl)-1 H -pyrazolo[3,4- d ]pyrimidin-1-yl)ethyl)-5 -chloro-3-phenylquinazoline-4(3 H )one methanesulfonate and a preparation method and use of the crystal form. The crystal form of the casein kinase 1ε inhibitor compound of the present disclosure has good water solubility and oral absorption, and can be better used for the treatment of malignant tumors and autoimmune diseases that benefit from the inhibition of casein kinase 1ε activity.