Abstract: Objective: To raise the recognition of tumors of hematonoietic system with serous cavity hydrops as the initial symptom.Methods: The clinical data of 19 cases of hematological system tumor with serous cavity hydrops as the initial symptom were analyzed retrospectively.Results: Nine cases were lymphoma (47.37%) of which, 7 were diagnosed by bone marrow cytomorphologic examination, one by biopsy of lymph node and one by examination of exfoliative cytology;4 cases (21.05%) were acute leukemia, 4 (21.05%) were chronic leukemia, and 2 (10.53%) multiple myeloma.All were confirmed by bone marrow cytomorphologic examination.Conclusions: The patients with hematonoietic system tumor with serous cavity hydrops as initial symptom are easily misdiagnosed.Bone marrow cytomorphologic examination, examination of esfoliative cytology and biopsy of lymph node should be resorted to for final diagnosis.