The invention relates to a crystalline of a cyclin-dependent protein kinase inhibitor and preparation methods thereof. Specifically, the invention relates to form II crystal of cyclin-dependent protein kinase inhibitor (CDK4&6) and preparation methods thereof. More specifically, the present invention relates to form II crystal of 6-acetyl-8-cyclopentyl-5-methyl-2-((5-(piperidin-4-yl)pyridin-2-yl)amino)pyrido[2,3-d]pyrimidin-7(8H)-one (compound of formula (I)) and preparation methods thereof. The form II crystal in this invention has X-ray powder diffraction pattern as shown in Figure 1. The form II crystal in this invention has good polymorph stability and chemical stability, furthermore, the solvent used for crystallization is low toxicity and low residual, so it can be better used for clinical treatment.本發明涉及一種週期素依賴性蛋白激酶抑制劑的結晶形式及其製備方法。具體而言,本發明涉及一種週期素依賴性蛋白激酶(CDK4&6)抑制劑的II型結晶及製備方法。具體地,本發明涉及6-乙醯基-8-環戊基-5-甲基-2-((5-(哌啶-4-基)吡啶-2-基)胺基)吡啶並[2,3-d]嘧啶-7(8H)-酮(式(I)化合物)的II型結晶及其製備方法,所述結晶具有如第1圖所示的X-射線粉末衍射圖譜。本發明所得到式(I)化合物的II型結晶具備良好的化學穩定性和晶型穩定性,並且所用結晶溶劑低毒低殘留,可更好地用於臨床治療。由於本案的圖為試驗數據,並非本案的代表圖。故本案無指定代表圖。
