The wire was made by Tungsten Carbide(WC) particles as core. MIG welding was used to surface iron-based WC wearable composite coating of different size and content of WC particles on mild steel. Microstructure was investigated. Surface rigidity and wear resistance were tested. The results indicate that the small particles are dissolved seriously, which separate out with reticulation. The hardness and wear resistance of the matrix are relative higher. The big particles are dissolved less, tree crystal separates out along particles. The particles are easy to fall off when wearing. So the hardness and wear resistance of the substrate are relative lower. The admixture with 80% big particles and 20% small particles has the best wear resistance, its wear resistance can achieve quintupling of quenching 45 steel. The hardness and wear resistance increase with content of WC increasing.