The KatG gene of Mycobacterium Tuberculosis has been associated with isoniazid (INH) drug resistance. While isoniazid (INH) considered as corner stone and main chemotherapy used throughout the world to manage tuberculosis, thus the Progress in apprehension of principle concepts associated with resistance to isoniazid (INH) has allowed molecular tests in addition to bioinformatics tool for the detection of drug-resistant tuberculosis to be developed. In Consecutive isolates (n = 20) of multidrug-resistant Mycobacterium tuberculosis, part of the katG was sequenced for INH resistance analysis. BLAST analysis of all sequences revealed 100% identity with the available strain "EGY-K361" Mycobacterium tuberculosis with Accession No: KC49137.1 except 6 isolates :isolate1, 2, 4, 11, 15, and isolate 20 revealed 99% identity. Thosesix isolates (30%) have detected mutation in Catalase-peroxidase enzyme S315T; three isolate from six 3/6 (50%) of mutant isolates have SNP AGC>ACC substitution while others 3/6 have substitution C>G in position 1280 which may contributed in altering gene expression. The secondary structure of wild and mutant proteins had been done using phyre2 software while the three dimensional structures of them had been done by Chimera software. Stability of mutant protein was increased which detected by i-mutant. Phylogenetic tree of the sequences revealed two distinct phylogroups: mutant isolates and wild isolates phylogroups with controls from different countries retrieved from Gene bank. Serine at position 315 is one of potential drug active sites that proved via SiteEngine soft ware, therefore any substitution will change efficiency of INH.