The present invention relates to a polymorph of a compound (3R,6S)-6-aminosulfonylamino-1-(thiazol-2-yl)-3-(2,3,4-trifluorophenyl)-3,5,6,7-tetrahydropyrrolo[1,2-c]pyrimidin-4-methyl formate (compound 1). The present invention further relates to a pharmaceutical composition and pharmaceutical use of the polymorph of compound 1, and a preparation method for the polymorph of compound 1.