The application of plasma-MIG hybrid welding technology in narrow groove welding is studied in this paper.Using numerical simulation technology, the combined heat source model of rotating body + double ellipsoid is applied to simulate the welding temperature field. The differences of weld shape and welding temperature field of welded joint between plasma-MIG hybrid welding and traditional MIG welding are analyze and compared. Experimental and numerical simulation results show that both the plasma-MIG hybrid welding and traditional MIG welding can provide wellformed joints. The plasma-MIG hybrid welding has smaller weld and heat affected zone area and higher welding efficiency than those of the traditional MIG welding. The numerical simulation is in good agreement with the experimental results. The combined heat source model can well reflect the heat input characteristics of plasma-MIG hybrid welding.