In the battle to phages, bacteria have evolved many immune mechanisms involved in the prevention of phage DNA entry, the degradation of entered DNA, and the limitation of the phage spreading at the cost of host cell death. An immune system in bacteria is formed by the collaboration of multiple immune mechanisms. In this paper, we reviewed the latest research progress of bacterial immune system and focused on the analysis of the operation mode of bacterial immune system and the evolution relationship between this system and phages.