The present invention relates to a hydroxyethyl sulfonate of cyclin-dependent protein kinase inhibitor, a crystalline form thereof and a preparation method therefor. Specifically, the present invention relates to 6-acetyl-8-cyclopentyl-5-methyl-2-((5-(piperidin-4-yl)pyridin-2-yl)amino)pyrido[2,3-d] pyrimidin-7(8H)-one hydroxyethyl sulfonate (compound of formula (I)), a crystal type I thereof and a preparation method therefor. Crystal type I of the compound shown in formula (I) obtained by the present invention has good chemical stability and crystalline stability, and has low toxicity and residue with respect to the solvent used for crystallization. Therefore, the crystal type I can be used in clinical therapy better.