Abstract: Spatters in laser penetration welding of aluminum alloys affects the process stability and reflects the laser welding process to a certain degree. The spatter characteristics in CO₂ laser and fiber welding of 6061-T6 aluminum alloy were investigated, and the reasons for the difference in spatter characteristics were discussed. Dynamic behavior of spatters was recorded in real-time by a high-speed camera. The spatter particles were captured and their sizes were measured experimentally. Probability density functions (PDFs) about the spatter velocity and size were fitted by Ordinary Least Squares (OLS) method in X² test. The result indicates that the spatter speed follows Gaussian distribution and the particle size follows lognormal distribution in both cases. However,the statistical speed of spatters is faster in fiber laser welding,which indicates that more attention should be paid to protect the focusing system. Moreover,the statistical diameters of the spatter particles are smaller and PDFs of the particle size is more fit with Lognormal distribution in fiber laser welding,which means that fiber laser welding process is more stable than CO₂ laser welding process.