Objective: To investigate the antitumor activities and apoptosis mechanisms of 3,7-dinitrodibenzobromonium salt (cBr) on human chronic myelogenous leukemia K562 cell line in vitro. Methods: The antitumor activities of cbr were tested by Trypanblau exclusion test, MTF coloretric assay and clonal forming test, and the mechanisms were studied by morphological analysis (microscopy, fluoreseencemicroscopy, electron microscopy) and flow cytometry analysis. Resuits: cBr could inhibit of the proliferation K562 cells and kill them significantly. The effects varied with different time and doses, and IC50 of cell colony forming rate was 0. 497 mmoL/L. Apoptosis rate tested by flow cytometry was 70.34%,and apoptotic characteristics could be found by microscopy and electron microscopy. Conclusion: cBr could inhibit K562 cell proliferation greatly, and could induce K562 cells into apoptosis.