The characteristics of both laser beam and TIG arc are investigated during the interaction between the vertical incident laser and TIG arc by using a laser power meter, a beam quality diagnosis instrument and a high speed camera. The experimental results demonstrate that, when CO2 laser beam passes through TIG arc, the laser power is attenuated dramatically, the beam is defocuses and even a laser supported combustion wave is generated. In this case, the beam quality is seriously worsened. On the other hand, the arc voltage is dropped and the arc column is expanded. However, the beam power, beam diameter, arc voltage and arc column seldom change during TIG arc interacted with YbYAG laser. Under the experimental conditions, the inverse bremasstrahlung absorption coefficient calculated is 14.14～26.29 m-1 for CO2 laser, 1.1～2.03 m-1 for YAG laser and the refractive index is 0.99249～0.99454 for CO2 laser, 0.99992～0.99994 for YAG laser, respectively. The inverse bremsstrahlung absorption coefficient for YAG laser is two orders of magnitude lower than that for CO2 laser. Meanwhile, there is less difference between the refractive index of YAG laser-TIG and YAG laser-air, so there is no obvious refraction of the TIG arc to the YAG laser, which is the main reason for the great difference between the CO2 laser-TIG and YAG laser-TIG interaction.