The present invention relates to the crystal form I of salt of a dipeptidyl peptidase-IV inhibitor, and the preparation method and use thereof. In particular, it relates to the crystal form I of dihydrochloride salt of the compound (R)-2-[[7-(3-aminopiperidin-1-yl)-3,5-dimethyl-2-oxo-2,3-dihydro-1H-imidazo[4,5-b]pyridin-1-yl]methyl]benzonitrile represented by formula (1), which is a dipeptidyl peptidase-IV inhibitor, and the preparation method and use thereof. The crystal form I of dihydrochloride salt of the dipeptidyl peptidase-IV inhibitor represented by formula (1) is characterized in that it has characteristic peaks at 8.7±0.2°, 19.4±0.2°, 23.5±0.2° and 27.2±0.2° in X-ray powder diffraction indicated by an angle 2θ (°) using Cu—Kα irradiation.