A simple and economic atmospheric plasma spraying method for thermal barrier coatings (TBCs) preparation on the mold cavity was developed to improve the injection parts properties. 7 wt% yttria stabilized zirconia was used as spray material with polyamide 11 (PA 11) as pore-forming agents to improve the coating properties. The effect of PA 11 powder contents on the microstructure, thermal conductivity, bonding strength and hardness of TBCs were studied. The results show that the thermal conductivity of TBCs decreased with the addition of PA 11, and the bonding strength reached maximum of 21.38 MPa with 10% PA 11 addition. Further studies confirm that TBCs were able to maintain a high and stable temperature in the mold cavity due to its low thermal conductivity, validated by the elimination of the welding line. With TBCs, the average tensile strength and elongation at yield of the injection parts increased by 25.6% and 128%, respectively.