To explore the relation of the serum level of sIL-2R in relapse patients with acute lymphoblastic leukemia (ALL).With ELISA, we determined the levels of sIL-2R of 48 patients with ALL after their first diagnoses, complete remission 1 and relapse. The levels of sIL-2R of 30 patients from complete remission 1 to relapse were monitored.The levels of sIL-2R were higher in the relapse group and first diagnosed group than in the control. The levels of sIL-2R were higher in the relapse group and first diagnosed group than in the complete remission 1 group. However, the difference between the complete remission 1 and the control had no statistical significance. When we determined the levels of sIL-2R dynamically, we found that after complete remission, the levels of sIL-2R decreased, however, before one month of hematological relapse, the levels of sIL-2R increased.Monitor of the level of sIL-2R can predict impending relapse of patients with ALL and is helpful to early diagnosis of relapse.