The 5’ and 3’ regions of nitrate reductase（NR） gene came from Beauveria bassiana D1-5 strain,NR1 and NR2 were amplified and cloned from the fungal genomic DNA,by designed primers according to the sequence published on NCBI.Homologus recombination vector was constructed successfully in order to knock out B.bassiana NR gene,verify the biological function,and build the technical system for gene knockout by homologus recombination.