Objective： To observe an abnormal expression of humoral immune response induced by memory B cells in tonsils and peripheral blood of patients with IgA nephropathy (IgAN), the variation of memory B cells after tonsillectomy, and to discover the role of tonsillectomy in IgAN.  Methods: In the study, 28 patients were diagnosed as IgAN via renal biopsy, and 27 patients suffering from chronic ton-sillitis without nephritis and 10 normal human beings were selected as controls. The expression of memory B cells in the tonsils and peripheral blood was tested by flow cytometry, and the same method was used to test the variation of the expression of memory B cells in peripheral blood of patients with IgAN after tonsillectomy. Results: In this study, higher percentages of memory B cells were observed in tonsil and peripheral blood of IgAN patients, which were 5.72%±5.26%, 4.92%±5.10%. After tonsillectomy, the percentage of memory B cells was 1.10%±0.65%, lower than that before tonsillectomy (P<0.05). Meanwhile, in tonsils and peripheral blood, the percentage of memory B cells varied with the variation of the urinary findings of the IgAN patients. Conclusion: The percentage of memory B cell in tonsils and peripheral blood could predict disease progression of IgAN to a certain extent.