The fiber laser was used to weld the TA15 titanium alloy skin grid structure, and the coaxial high-speed camera monitoring scheme was used to collect images and extract features of the molten pool morphology under different welding parameters. The results show that the segmentation extraction method of molten pool edge based on brightness features can solve the problem of uneven brightness before and after the molten pool image, and extract accurate molten pool edge information. The molten pool width and drag angle have a strong correlation with the weld joint width, and the length, width, and drag angle of the molten pool have a strong correlation with the weld penetration. At the same time, a regression analysis model of welding process parameters and weld formation is established, and the weld forming size is predicted. The average prediction errors of the weld joint width and weld penetration are 0.14 mm and 0.10 mm, respectively.