The wire was made with foundry tungsten carbide particles as core. Iron-based tungsten carbide wearable composite coatings of different granularity and content on mild steel were prepared by the method of MIG welding. Microstructure of the welded coating was investigated. Surface hardness and wear resistance to rubber wheel were tested. The results indicate that the small particles dissolved more, which separate out with net on crystal boundary. As a result the hardness and wear resistance of that matrix are relative higher. The big particles dissolved less and tree crystal separates out along particles. The gaps of particles are big and the particles tend to fall off when the coating is worn. So the hardness and wear resistance of the matrix are relative lower. The admixture with 80% big particles and 20% small particles has the best wear resistance and its wear resistance is quintupling of that of quenched 45 steel. With particles content up to 50wt%, the hardness and wear resistance increase. The wire was made with foundry tungsten carbide particles as core. Iron-based tungsten carbide wearable composite coatings of different granularity and content on mild steel were prepared by the method of MIG welding. Microstructure of the welded coating was investigated. Surface hardness and wear resistance The results indicate that the small particles dissolved more, which separate out with net on crystal boundary. As a result the hardness and wear resistance of that matrix are relative higher. The big particles dissolved less and tree crystal separates out along particles. The gaps of particles are big and the particles tend to fall off when the coating is worn. So the hardness and wear resistance of the matrix are relative lower. wear resistance and its wear resistance is quintupling of that of quenched 45 steel. With particles content up to 50 wt%, the hardness and wear resistance increase