Objective:To study the characteristics of drug-resistant genetic mutation of rpoB on coal workers’ pneumoconiosis complicated with L-form of Mycobacterium tuberculosis. Methods: A total of 42 clinical isolated strains of Mycobacterium tuberculosis L-forms were collected

including 31 drug-resistant strains. Their genomes DNA were extracted

the target genes were amplified by PCR

and the hot regions in the rpoB gene were analyzed by automated DNA sequenator. Results: No mutation of rpoB gene was identified in 11 rifampicin-sensitive strains while conformation changes were found in 31 rifampicin-resistant strains. The mutation rate was 93.55% （29/31） in resistant strains

mainly concentrated in codon 531 （51.6%

16/31） and 526 （32.26%

10/31）. Base substitutions happened

including 27 unit point mutation and 2 two point mutation. The mutation of codon 516 that new found wasn’t reported by internal and overseas scholars. Conclusion: The substitution of highly conserved amino acids encoded by rpoB gene results in the molecular mechanism responsible for rifampicin resistance in Mycobacterium tuberculosis L-forms. It also proves that rpoB gene is diversiform.