Abstract: Objective :To study the value of flow cytometry (CD45/SSC gate) in detecting bone marrow involvement of malignant lymphoma. Methods :Paired data of chi-square test design was adopted. Bone marrow of malignant lymphoma patients was detected by Flow Cytometer and bone marrow smear was simultaneously performed. Results :The samples of the bone marrow in 34 patients with malignant lymphoma were examined by flow cytometer with smear. A total of 23 cases wire detected the bone marrow involvement by flow cytometry and only four were found with bone marrow invasion by means of smearo=17.05, P<0.05). Conclusions : flow cytometry is a feasible and effective method for detection in patients with bone marrow involvement. This method is super to conventional bone marrow smear.