Disclosed is an intermediate of bemaciclib (also referred to as abemaciclib) having a structure of Formula II, and preparation methods therefor. The preparation methods may comprise condensation, amidine reaction, cyclization and/or other unit reactions. Bemaciclib is obtained through a guanidination reaction and a cyclization reaction using the bemaciclib intermediate disclosed herein as a starting material. starting materials for the preparation methods disclosed herein are easily available, the procedures are simple, and the preparation methods are economical, environmentally friendly and suitable for industrial production.