The work aims to provide theoretical basis for avoiding corrosion of aluminum alloy workpieces during cutting process by studying the effect of microorganisms breed in cutting emulsion on the corrosion behavior and corrosion laws of aluminum alloy. Surface morphology observation and composition analysis methods are used to study the effect of microorganisms on the corrosion morphology of aluminum alloy and the composition of corrosion product, respectively. The distribution of pitting corrosion on the surface of aluminum alloy is analyzed by statistical method. Finally, the electrochemical characteristics of aluminum alloy surface are analyzed by electrochemical method. In the cutting emulsion containing microorganisms, the corrosion of aluminum alloy workpieces is more serious. The surface of the aluminum alloy is attached by microorganisms, forming uneven corrosion product films and biofilms. After removing the film, obvious pitting pits are found, and the number and depth of pitting pits are large, with the deepest reaching 17.7 μm. However, in the sterilized cutting emulsion, only the emulsion is attached to the surface of the aluminum alloy, which is relatively uniform. After removing the film layer, the surface scratches is obvious and no pitting. The electrochemical results also showed that in the cutting emulsion containing multiple microorganisms, the charge transfer resistance Rct of the aluminum alloy decreased gradually from 23 kΩ when immersed for 3 days to 8.3 kΩ after being immersed for 15 days, indicating that the corrosion rate of aluminum alloy significantly increase with time. The growth of microorganisms in the cutting emulsion significantly accelerate the corrosion of the aluminum alloy.