A series of novel, highly potent, selective inhibitors targeting both CDK4/9 and HDAC1 have been designed and synthesized. N1-(4-((7-Cyclopentyl-6-(dimethylcarbamoyl)-7 H-pyrrolo[2,3- d] pyrimidin-2-yl)amino)phenyl)- N8-hydroxyoctanediamide (6e) was discovered. The lead compound 6e with excellent CDK4/9 and HDAC1 inhibitory activity of IC50 = 8.8, 12, and 2.2 nM, respectively, can effectively induce apoptosis of cancer cell lines. The kinase profiling of compound 6e showed excellent selectivity and specificity. Compound 6e induces G2/M arrest in high concentration and G0/G1 arrest in low concentration to prevent the proliferation and differentiation of cancer cells. Mice bared-breast cancer treated with 6e showed significant antitumor efficacy. The insight into mechanisms of 6e indicated that it could induce cancer cell death via cell apoptosis based on CDK4/9 and HDAC1 repression and phosphorylation of p53. Our data demonstrated the novel compound 6e could be a promising drug candidate for cancer therapy.