Abstract: Objective: To observe the change of minimal residual disease (MRD) in acute leukemia patients in remission,and explore the relationship between MRD and the prognosis.Method: Sixty-two cases of adult acute myeloid leukemia (ALL) with complete response (male 34,female 28) and 126 cases of adult acute myeloid leukemia (AML) with complete response (male 67,female 59) were enrolled.We used flow cytometry technology (FCM) to detect MRD in bone marrow,and the results were compared with traditional bone marrow cell morphology.After average 6-month follow-up (3 to 24 months) of all the patients,we recorded the changes of MRD value and prognosis including relapse and relapse time,relapse rate among different gender,age and refractory status.Result: In 174 bone mallow samples of ALL patients,MRD were positive in 146 samples,including 31 samples with MRD ≥ 0.05,and 28 samples with MRD<0.001 (MRD negative).Twenty-four patients were diagnosed as relapse by bone marrow cell morphology,of which 18 were finally diagnosed as relapse 9 to 24 months (average 6 months) after continually positive in MRD.The average sensitivity of MRD assay in predicting relapse were all 100% and the specificity were 76.9% in 1 to 12 months group,and 77.8% in 13 to 24 months group,showing no significant difference between two groups (P>0.05).A total of 126 patients with AML in complete remission detected MRD 126 times,of which 21 patients were diagnosed as relapse by bone marrow cells morphology.ALL and AML patients with MRD>0.001 had obviously higher recurrence rate,and the recurrence rate had no relation with the gender,age and refractory (P>0.05).MRD ≥ 0.01 patients had significantly shorter relapse time than MRD ≤ 0.005 and 0.005Conclusion: Relapse of acute leukemia can be predicted by MRD detection with the use of FCM.MRD can be used as a sensitive index for the evaluation of prognosis.When MRD is higher than 0.001,the risk of relapse is higher.Continuous dynamic monitor of MRD has important significance in predicting the recurrence and prognosis and directing the individualized treatment.