The invention provides a 1,2-diol compound type II single crystal preparation method, which comprises: dissolving (1S,2S,3R,5S)-3-(7-{[(1R,2S)-2-(3,4-difluorophenyl)cyclopropyl]amino}-5-(propylthio)-3H-1,2,3-triazolo[4,5-d]pyrimidine-3-yl)-5-(2-hydroxyethoxy)-cyclopentane-1,2-diol and a compound represented by a formula I in an organic solvent, adding an anti-solvent, and crystallizing. Accordingto the present invention, the preparation method has simple operation, and the obtained product has a single crystal form, does not contain other non-target crystal forms, and has high application prospect.