In order to breed the penicillin high producing strain, the Penicillium Chrysogenum 10-2-12 was adopted to mutate by high energy electrons mutation. The mutant 13-6-55 was screened through 18 batches, the titer of the mutant 13-6-55 was 8.2% higher than the titer of the Penicillium Chrysogenum 10-2-12, and the genetic stabilization of the mutant 13-6-55 was fine. The average titer in fermentor was increased 3.6%.