The invention relates to the technical field of flattening equipment, in particular to an automatic coil feeding device for uncoiling a steel coil. The automatic coil feeding device comprises a base,a controller, a feeding mechanism, a heating mechanism and a conveying mechanism; and the feeding mechanism comprises a sliding table, a rotating assembly and a plurality of tightening assemblies, theheating mechanism comprises a heating table and a heat supply assembly, the conveying mechanism comprises a traction assembly, a flattening assembly and a compaction assembly, the traction assembly and the flattening assembly are symmetrically arranged at two ends of the heating table, the compaction assembly is arranged at the side of the flattening assembly, and the rotating assembly, the heatsupply assembly, the traction assembly, the flattening assembly, the compaction assembly and the plurality of tightening assemblies are all electrically connected with the controller. According to theautomatic coil feeding device for uncoiling the steel coil, the steel coil can be effectively and fixedly arranged, thereby preventing the steel coil from falling off and ensured not to be polluted when the internal stress of the steel coil is eliminated, thereby facilitating the subsequent production and use.