Objective:To evaluate systematically the association between the c. 415>C polymorphism of NUDT15 gene and the toxicity of 6-mercaptopurine(6-MP)in children with acute lymphoblastic leukemia(ALL).Methods:The literatures in domestic and foreign databases were retrieved: PubMed, EmBase, Cochrane Library, CNKI, CBM, VIP Chinese Sci-tech Journal Database, and Wanfang Database.The language was limited to Chinese or English.A case-control study or cohort study of 6-MP treatment in pediatric ALL related to the toxicity of the NUDT15 gene c. 415>C polymorphism was included.The time of search was set from the establishment of the database to October 1st, 2020.Two researchers screened the literature independently, extracted data from the literature that met the inclusion criteria, and evaluated the quality of the included studies.The association between locus polymorphism and toxicity during 6-MP chemotherapy was analyzed by Meta analysis with Rev Man 5.3 and Stata 12.0 software.Results:Nine studies were finally included, eight of which were cohort studies and one was a case-control study, with a total of 1 068 patients.The results showed that under the five genetic models, the mutation at c. 415>C of NUDT15 gene was significantly associated with the risk of leukopenia and neutropenia( P<0.01), while hepatotoxicity was with no significant association between the occurrence risk of damage( P>0.05). Conclusion:The mutation at c. 415>C of NUDT15 gene significantly increased the incidence of leukopenia and neutropenia during 6-MP chemotherapy, while there was no significant effect on the occurrence of hepatotoxicity.