Histone deacetylase (HDAC) inhibitors of cyclic peptide have been proved to be the most complex but themost stable and relative efficient inhibitors because of their large cap region. In this paper, a series of studieswere carried out to evaluate the efficacy of synthetic bicyclic tetrapeptide inhibitors 1-5 containing hydroxamicacid referring molecular docking, anti-proliferation, morphology and apoptosis. Docking analysis, togetherwith enzyme inhibitory results, verified the selective capability of inhibitor 4 to HDAC4, which might closelyrelated to haematological tumorigenesis, with Phe227, Asp115, Pro32, His198 and Ser114 participating intohydrophobic interactions and Van der Waals force which was familiar with former study. Moreover, inhibitor4 inhibited K562 cell line at the IC50 value of 1.22 μM which was 51-67 times more efficient than that for U937and HL60 cell lines. Inhibitor 4 exhibited the cell cycle-arrested capability to leukemia at S phase or G2/Mphase as well as apoptosis-induced ability in different degrees. Finally, we considered that bicyclic tetrapeptideinhibitors were promising inhibitors used in cancer treatment and inhibitor 4 could prevent K562 cell line wellfrom proliferation, arrest cell cycle and induce K562 towards apoptosis to achieve the goals of reversing cancercells which could become a potential leukemia therapeutic agent in the future.