L-arginine is a semi-essential basic amino acid in human bodies and animal bodies, and has multiple unique physiological and pharmacological effects. The invention mainly aims at knocking out a competitive bypass metabolism key enzyme gene for proline synthesis, wherein a corynebacterium crenatum genome serving as a template is subjected to PCR (polymerase chain reaction) amplification respectively by using upstream and downstream primers of a proB gene, and is used for preparing a deletion type gene proB' by utilizing overlap PCR amplification; recombinant plasmid pK18mobsacB-proB' is connected and electroporated to enter the corynebacterium crenatum, and a secondary homologous recombination gene deletion type strain is screened; the recombinant strain corynebacterium crenatum delta proB is subjected to a flask shaking experiment, and functions of the proB gene in the corynebacterium crenatum are lost, so that the capability of proline synthesis is greatly reduced, and sugar consumption can be improved; and the accumulation of proline in the fermentation broth is only 2.7 percent of that of a control strain, so that the yield of target amino acid L-arginine can be improved.