40 samples were collected from milk from Homs to isolate the bacteria and study their ability to produce the enzyme β- galactosidase and diagnose isolates the most efficient in the production of the enzyme, the results showed the presence of 25 sporeforming isolates producing the enzyme β-galactosidase , the effectiveness of β-galactosidase was estimated using spectrophotometer at a wavelength of 420 nm.