Objective To defect the level of platelet antibody-IgG (PA-IgG) in patients with congestive splenomegaly and hypersplenism and the change of PA-IgG level after splenectomy and subtotal splenectomy. Methods Twenty four cases of congestive splenomegaly and hypersplenism were investigated. Results The level of PA-IgG in 24 cases were higher than normal range (Ｐ＜0.01), while the platelet count were lower than normal range and there was a significant negative correlation between the level of PA-IgG and platelet count (r＝-0.4747, Ｐ＜0.05). After subtotal splenectomy or splenectomy, the level of PA-IgG descended, the platelet count raised and the negative correlation between the level of PA-IgG and platelet count disappeared. Conclusion The results suggest that there is a immunoregulation between PA-IgG and platelet. Perhaps spleen has some relation with the immunoregulation.