Abstract： AIM: To analyze the character of rpoB genemutation in rifampin (RIF)-resistant Mycobacterium tuberculosis (M. TB) strains isolated from tuberculosis patients in Xi'an and to develop and evaluate methods to detect the RIF-resistant gene of M. TB. METHODS: RpoB gene mutation was examined in 120 M. TB strains (81 RIF-resistant and 39 RIF-sensitive) isolated from tuberculosis patients in Xi'an by polymerase chain reactionsingle strand conformation polymorphism (PCR-SSCP) and multiplex allele specific polymerase chain reaction (MAS-PCR). RESULTS: By PCR-SSCP, the ratio of rpoB mutation in RIF-resistant M. TB strains was 85% (69/81) and there was only 1strain with rpoB mutation in the 39 RIF-sensitive M.TB strains. By MAS-PCR, the ratio of rpoB gene mutation in RIF-resistantM. TB strains was 93% (75/81) and no rpoB gene mutation was found in the 39 RIF-sensitive M. TB strains. The ratio of rpoB gene mutation point at codon 531, codon 516 and codon 526 was respectively 45% ( 34/75 ), 24% (18/75) and 20% ( 15/75 ). CONCLUSION: RIF resistance of M. TB strains isolated from tuberculosis patients in Xi'an is correlative with rpoB gene mutation. Detection of rpoB gene using MAS-PCR can be a simple, rapid and accurate method for the early diagnosis of RIF-resistant M.TB.