In order to investigate the patterns of FIX gene mutation in 3 unrelated hemophilia B (HB) patients, the activated partial thromboplastin time (APTT) and FIX activity (FIX: C) tests were adopted for phenotype diagnosis. All of the eight exons and their flank of FIX gene were amplified by polymerase chain reaction (PCR), the nucleic acid sequences were detected by dideoxymediated chain-termination method. The results indicated that as compared with normal control, the APTT value significantly increased, FIX: C value obviously decreased, PT value was normal. Sequencing results showed that all of 3 HB patients had the changes of gene sequences, among 3 patients the G22119A point mutation of exon 6 existed in case No.1, the G7932C point mutation of exon 2 was detected in case No.2 and the T32685C point mutation of exon 8 was found in case No.3. In conclusion, the relevant changes of gene sequences in all of 3 HB patients were detected, which provides some evidences for molecular mechanism of gene deficiency in HB patients.