A high speed tandem TIG welding process was adopted to manufacture titanium welded tubes. A coupled electrode, arc and weld pool numerical model was also developed to investigate the temperature distribution, arc plasma and molten metal flows, and energy propagation of this welding process. Under the driving of the electromagnetic force, arc plasmas under the leading and trailing electrodes flowed towards each other. The Marangoni stress was much higher than the arc shear stress, and was the main driving force for the backward molten metal flow on the top weld pool surface. The calculated arc efficiency of this welding process was 79.8%. The high speed tandem TIG welding process can improve the manufacturing efficiency and quality of titanium welded tubes.