Plasma-MAG hybrid welding method and ordinary MAG welding method were used respectively to carry out the welding tests of SUS301L-MT stainless steel middle heavy plates for railway vehicles under the condition of ER308 LSi welding wire and φ（Ar）98%+φ（CO2）2% shield gas selected. The pulsating tensile fatigue test and the fatigue strength estimation were conducted on the butt welded joints and the cruciform joints of plasma-MAG hybrid welding and ordinary MAG welding respectively. The results indicate that the median fatigue strength in fatigue life of 2×106cycle is 279 MPa and 160 MPa for the butt joint and the cruciform joint of plasma-MAG hybrid welding respectively. Compared with ordinary MAG welding, the fatigue strength of plasma-MAG hybrid welded joints increases, in which the fatigue strength of butt joint is higher than that of cruciform joint.