The invention relates to a titanium heat exchanger welding process and tools thereof. A titanium heat exchanger comprises pipe boxes, a shell, heat exchange pipe bundles and pipe plates. Titanium materials are adopted for the pipe boxes, the heat exchange pipe bundles and the pipe plates. Titanium material welding seams of the titanium heat exchanger include longitudinal seams of cylinders of the pipe boxes, circular seams of the cylinders of the pipe boxes and end sockets of the pipe boxes, and fillet welds between heat exchange pipes and the pipe plates. The welding process includes the steps of before-welding preparation, the during-welding process and after-welding inspection. When the longitudinal seams and the circular seams are welded, the front protection tool is arranged in front of a welding gun, the welding seam front face protection tool is arranged behind the welding gun, and the welding seam back face protection tool is arranged on the back faces of the welding seams. When the fillet welds are welded, the pipe plate fillet weld protection tool is adopted. The tools include the pipe plate fillet weld protection tool, the front protection tool, the welding seam front face protection tool and the welding seam back face protection tool. Various gas shield tools are adopted for the welded positions of the titanium heat exchanger to protect the welding seams, the welding seam quality is improved, and it is ensured that the welding seams meet the standard requirement.