Abstract: Taking erythromycin producing strain, Streptomyces erythreus as research object, the effects on Streptomyces erythreus caused by three different mutantion ways of LiCl, UV and ion beam were explored. The mutated conditions were optimized by survival rate and mutation rate. The optimum mutation concentration of LiCl is 1.2%, the proper mutation time of UV is 120 s, and the optimal fluence of ion beam is 200×1014 cm－2. Then the three ways were combined to do compound mutation. One highyield mutant E03171726 by compound mutation was obtained. The titer of the strain is 7 126 μg/mL, which is nearly 20.3% higher than that of original strain E03. Several passages and separation experiments show that the genetic stability of the mutants is good enough.