Objective To investigate the distribution and significance of CD20 positive cells in the early human embryo. Methods Distribution and morphology of CD20 positive cells in 10 specimens of human embryo aged from 6 to 7 weeks were brown, and studied with immunohistochemical method. Results 1. CD20 positive cells appeared in the liver of early human embryo.2. The immunohistochemical positive substances were brown, and found chiefly in the nuclei of B cells as unevenly-distributed granules,and were not detected in the cytoplasma and on the cell membrane.Conclusion The accuracy of location and distribution of CD20 positive cells in the nuclei of B cells of early human embryo liver may provide an important clue for further exploration of the functional mechanism of CD20 in the process of B cell proliferation and differentiation.