To investigate the correlation between cytotoxic T lymphocyte antigen-4 (CTLA-4) gene polymorphism and children with acute lymphoblastic leukemia (ALL). A total of 86 children of ALL (23 HR, 54SR) and 112 healthy controls was selected. The genptypes were determined by means of polymerase chain reaction (PCR) and the PCR product sequencing. Genotype and alleles frequency of SNP-318, SNP+49 and SNP-CT60 were compares among different groups. The frequency of TC, TT genotype and T allele in ALL children at SNP-318 position were statistically higher than controls. In HR group, the frequency of TC, TT genotype at SNP-318 position was statistically higher than SR group. There was no significantly difference in genotype and allele distribution of SNP+49 position among the HR patients, SR patients and control group. (2) The frequency of GG genotype and G allele in ALL children at SNP-CT60 position were significantly higher than controls. The genotype and allele distribution of SNP-CT60 position between different clinical risk groups were no significantly different. As a result of the increased frequency of TC, TT genotype and T allele at SNP-318, ALL children synthesized more CTLA-4 to deliver the inhibitive signal, and this lead to restraint of T cell activation. Such difference at SNP-318 position was obvious in HR children. The SNP+49 position is probably not the main regulating point in ALL. (2) In SNP-CT60 position, the G allele played the main part. The increase of G allele frequency result in the high expression of CTLA-4. such difference at SNP-318 position was obvious in HR children.