The invention particularly relates to antibacterial stainless steel and a preparing method thereof. According to the technical scheme of the antibacterial stainless steel and the preparing method thereof, stainless steel obtained after surface pretreatment is put into a dopamine buffer solution to be deposited for 0.1 h to 72 h under the condition with the temperature ranging from -5 DEG C to 40 DEG C; then the obtained stainless steel is put into a solution containing titanium ions to be deposited for 0.1 h to 6 h; and finally the obtained stainless steel is put into a solution containing silver ions to be deposited for 0.1 h to 6 h, and therefore the antibacterial stainless steel is obtained. The concentration of the dopamine buffer solution ranges from 0.01 mol/L to 1 mol/L, the concentration of the solution containing the titanium ions ranges from 0.001 mol/L to 1 mol/L, and the concentration of the solution containing the silver ions ranges from 0.001 mol/L to 1 mol/L. By means of the antibacterial stainless steel and the preparing method thereof, the technology is simple, environment friendliness is achieved, and the cost is low; the surface antibacterial nanometer film layer structure of the antibacterial stainless steel prepared through the method is well-defined and orderly, is firmly combined with a base material, is high in corrosion resistance and hardness and has good antibacterial performance both under the illumination condition and the non-illumination condition.