Aiming at the color change of two-dimensional code laser marking on the surface of titanium alloy, this paper uses the method of experimental characterization analysis to explore the color change mechanism of two-dimensional code laser marking on the surface of titanium alloy. The influence of laser power, scanning line spacing, laser frequency and scanning speed on the color change of two-dimensional code laser marking is studied respectively. The spectrophotometer, scanning electron microscope, optical microscope, energy spectrometer and other equipment are used to characterize and analyze the mechanism of color change. The results show that with the increase of laser energy density, the surface color after laser marking gradually becomes black. On this basis, the reflectivity of the incident light of the two-dimensional code marked under different laser parameter combinations is analyzed, and its microscopic morphology is observed and its surface composition is measured. It is found that the main reason for the color change of the two-dimensional code marking is that the change of the micro-morphology causes the change of the reflectivity of the incident light on the surface of the two-dimensional code marking, and the nitrogen oxides produced during the processing process show different colors and the film thickness formed by the nitrogen oxides is different, causing different color changes.