Adaptive laboratory evolution is an effective method to industrial microbial genetic breeding. In this study， Lactobacillus casei Zhang which was evolved in LSM medium with gentamicin to 1 200 generations， was used as the research object， continue to evolve in LSM medium without gentamicin to 1 000 generations. The change of cell morphology， viable count， turbidity， resistance phenotypic and genotype were tracked and monitored. The results showed that：①the cell morphology， viable count and turbidity and resistance phenotypic were stable； ② Only 11 mutations were detected in the genome， including 4 synonymous mutations and 7 non-synonymous mutations. Therefore， it can be considered that the strain has a good genetic stability.