A set of high-speed cameras were used to obtain the plasma image in different directions in the process of CO2 laser welding. The centroid projecting principle was employed to adjust the plasma images in different directions. The projection relationship between the 3D plasma and 2D images were achieved by camera calibration and calculation of projection weighting factors. Finally, the 3D radiation distribution of plasma was obtained based on algebraic reconstruction technology (ART). The result shows that the 3D reconstruction of laserinduced plasma has a high reconstruction accuracy. And compared with 2D plasma image, the 3D reconstructed data reflects the dimensional characteristics and inner information of the plasma much more accurately.