Objective To identify novel ABO allele in Chinese population. Methods The ABO blood group was tested by serological method, and then genotyped by sequence-specific primer (PCR-SSP) , gene cloning and sequence analysis. Results A healthy blood dornor who was diagnosed as having A2 subgroup and A2O1genotype was subjected to ABO gene cloning and sequence analysis. The haplotype-specific sequence analysis indicate that two single-base deletions, where G-deletion at nucleotide position 261 and A-deletion at nucleotide position 496 were determined in the O1 allele. The nucleotide sequence of the novelO1 allele were identical to ABO 0101 allele except for A-deletion at nucleotide position 496 in exon7 of ABO locus. Conclusion We defined this 0 allele as a novel O1 variant allele, and its registered number by GenBank is AY374123.