Abstract: The metal active-gas welding(MAG) experiment for welded joint of wear-resistant steel JFE-EH400 and cast steel ZG30 MnSi of scraper conveyors central groove in this study was carried out in super heavy coal mining machinery. The microstructure, defect characteristics,inclusion composition and microhardness distribution of base metal and welded joints were investigated by OM, SEM, EDS element mapping and microhardness test. The results indicatd that the microstructure of cast steel ZG30 MnSi was composed of tempered sorbite. And the microstructure morphology characteristics of wear-resistant steel JFE-EH400 presented alternate superposition distribution of ferrite + pearlite and precipitation strengthening layer. And the welded joint of JFE-EH400 and ZG30 MnSi was composed of acicular ferrite(AF), polygonal ferrite(PF) and a small amount of pearlite, the microstructure morphology of welded joint presented interlocking features on acicular ferrite phase.The relationship between the microhardness value of the welded joint was heat affected zone(HAZ)＞ base metal ＞ weld metal, and the high hardness points appeared in the HAZ near the overlap zone of the weld metal, the hardness values were as high as 329 HV 10 and 334 HV 10.For the welding production of the scraper conveyors central groove of the super heavy coal mining machinery, the bottom welding quality of the large-thickness medium plate JFE-EH400 and the ZG30 MnSi dissimilar steel was the key. The welding process often produced cracks and pore defects due to the falling molten pool of impurities and rusts. Before welding, the removal of impurities, rust, etc. from the cast steel and groove surface and the strict implementation of welding process parameters and specifications were one of the main measures to avoid and solve welding defects.