The work aims to explore the mechanism of triethanolamine (TEA) in the barrel finishing of aluminum alloy specimens. Barrel finishing experiments were carried out on aluminum alloy surface with different concentrations of triethano-lamine solution under the same conditions. Changes in roughness value of specimen before and after finishing were tested by a roughness measuring instrument. Changes in mass of specimen before and after finishing were tested by an electronic balance, and the material removal rates were calculated. The lattice distortion of the specimen surface was analyzed by X-ray diffractometer (XRD). The morphology of the specimen surface was analyzed by scanning electron microscope (SEM). The changes of the surface elements of the specimen were analyzed by energy dispersive spectrometer (EDS). At the initial stage of processing, the minimum variation ratio of roughness and the minimum material removal rate without the effect of triethanolamine were obtained. Ra value decreased from initial 1.245 μm to 0.934 μm and MRR was 0.223 mm3/min. The maximum variation ratio of roughness was obtained with the effect of triethanolamine of which the volume concentration ratio was 9%. Ra value decreased from initial 1.184 μm to 0.558 μm. The maximum material removal rate was obtained with the effect of triethanolamine of which volume concentration ratio was 5%. The material removal rate was 0.445 mm3/min. The maximum value of lattice distortion was 0.0045 and the minimum value of lattice distortion was 0.0008. After processing, the Si element was enriched on the specimen surface. At the initial stage of processing, the triethanolamine can improve the processing efficiency of aluminum alloy specimen. The surface activity of solids can be increased under the coupling effect by the liquid medium and the solid medium to the specimen, and the lat-tice distortion is produced on the specimen surface. Therefore, the mechano-chemistry effect is caused. The Si particles protects the Al base, and this phenomenon weakens the micro-grinding in the later processing. Therefore, the material removal rate and surface roughness keep constant value respectively.