High frequency hybrid twin-electrode TIG welding is a new type of welding method with high quality and efficiency. In order to study its arc behavior,the arc static characteristic and dynamic characteristic tests are designed by using high-speed photography technology to photograph arc profile. The high frequency pulse currents of 0～80 kHz are introduced in the arc static characteristic test.The results show that the hybrid arc shape with high frequency pulse current is obviously different from that without high frequency pulse current,and is symmetrical triangle on the whole, and the arc outer contour is more straight,the arc diameter is smaller. When the pulse current frequency is below 50 kHz,the higher the pulse current frequency,the greater the hybrid arc compression,and the higher the energy density and stiffness of the hybrid arc. The dynamic transition behavior of hybrid arc is studied by using the method of arc step-up,the results show that the hybrid arc has strong stability and high arc stiffness with the effects of cutting-edge,non-arc-jumping and high frequency self-localization,and its mechanism is deeply analyzed.