Understanding the physical characteristics of plasma of welding heat source contributes to its process optimization. In YAG laser+ double pulsed GMAW hybrid welding process,the laser beam and two arcs are in the same molten pool. The coupling effect of three heat sources with different properties makes the physical characteristics of plasma more complex in hybrid laser-double MIG welding than any other welding methods. The physical characteristics of hybrid plasma such as radiation intensity,electron temperature and electron density are studied based on spectroscopic technique combining with high-speed photography. The results show that there is no new spectral line after laser addition; radiation intensity is more intensive than that of double MIG welding. Arc column near the laser point on the surface of molten pool shrinks obviously under the influence of laser beam,the two arcs are drawn to close to laser beam according to the minimum voltage principle. Metal particles are ionized because of intense thermal effects and gather on the surface of the workpiece and near the laser beam. The electron temperature and density in the local area increase,providing an additional ionization channel for the arc,which makes the arc more stable.