Objective: It is hypothesized that benzene-induced hematotoxicity may be association with the production of reactive oxygen species (ROS). Here, we hypothesize that the ROS is a possible molecular mechanism of benzene-mediated modulation of hematopoietic progenitor/stem cells. Methods: Mice were injected subcutaneously with benzene (150 mg/kg) dissolved in corn oil. The control group was injected subcutaneously with corn oil. All mice were injected once a day, 5 days per week for 4 weeks. The number and the ROS level of Lin- cells, Lin-c-kit+ cells, Lin-sca-1+ cells, and Lin-c-kit+sca-1+ cells were analyzed by flow cytometer. Results: The percentages of Lin-c-kit+ cells and Lin-c-kit+sca-1+ cells were significantly decreased after benzene exposure. Furthermore, the ROS levels of Lin- cells, Lin- sca-1+ cells, and Lin-c-kit+ cells were increased in benzene-treated group than control group, though they did not show a significant change of ROS levels. However, a significant increase in the production of ROS in Lin-c-kit+sca-1+ cells was observed in benzene-treated group. Conclusion: It indicated that benzene exposure could induce the inhibition of hematopoietic progenitor/stem cells and a higher level of ROS in hematopoietic stem cells. The mechanism between higher ROS level and inhibition of hematopoietic stem cells induced by benzene was interesting and needed further explored.