Provided are a hydroxyethyl sulfonate of a cyclin-dependent protein kinase inhibitor, a crystalline form thereof and a preparation method therefor. Specifically, 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 form I thereof and a preparation method therefor are provided. Crystal form I of the compound of formula (I) has good chemical and crystalline stability, low toxicity, and low residual crystallization solvent. The compound of formula (I) and crystal form I thereof can be used in improved clinical therapy.