In　order　to　breed　a　mutant　strain　for　high　production　of　apramycin,　carbamoyltobramycin　biosynthesis　genes　tobS1-C　were　delected　from　Streptomyces　tenebrarius　through　homologous　recombination.　Gene　deletion　vector　pSH6　was　constructed　and　introduced　into　S.　tenebrarius　Tt49　through　conjugal　transfer.　TobS1-C　genes　in　the　chromosome　were　displaced　by　deletion　allele　on　the　plasmid　via　double　crossover.　Then　the　mutant　S.　tenebrarius　T103(ΔtobS1C)　was　proved　to　be　genetically　stable.　Shaking　flask　experiments　and　TLC　analysis　showed　that　the　mutant　strain　only　produced　apramycin.