Abstract: β-galactosidase, as a safe and nontoxic enzyme preparation, has been not only widely used in food industry and medical fields, but also has great application potential in biotechnology fields, such as enzyme engineering and protein engineering. Microbial fermentation, as a mainstream production method of β-galactosidase, still has some problems including long fermentation time and low extraction rate. While using the heterologous expression system of engineering bacteria to produce β-galactosidase shows the advantages of high expression quantity and low cost. This paper focuses on the gene source, expression host bacteria, expression methods of β-galactosidase heterologous expression system and its application value, to be aimed at providing scientific basis and theoretical reference for the development and utilization of novel β-galactosidase products.