Bacterial strain typing is an important process for diagnosis, treatment and epidemiological investigations. Current bacterial strain typing methods may be classified into two main categories: phenotyping and genotyping. Phenotypic characters are the reflection of genetic contents. Genotyping, which refers discrimination of bacterial strains based on their genetic content, has recently become widely used for bacterial strain typing. The methods already used in genotyping of bacteria are quite different from each other. In this review we tried to summarize the basic principles of DNA-based methods used in genotyping of bacteria and describe some important DNA regions that are used in genotyping of bacteria.