This paper studies of laser parameters for direct-part marking Data Matrix symbols on aluminum alloy by using Nd:YAG laser. Different laser parameters and the resultant can affect the barcode grade profoundly. The experiment focuses on all interval values of the vector step, inter-step time, laser Q frequency and laser Q release time. From the experiment results, the relationship between laser parameters and barcodes grade was found, and thus determined the optimal laser parameters. By analyzing the higher and the lower power density processing module SEM images and EDS data, it was found that the microstructure and micro-components of formations that created by the interaction between the laser and the aluminum alloy can affect the barcodes grade level significantly. We also found that the interaction between the laser and the aluminum alloy can be divided into four stages.