In this research, the combination of finite element simulation and 3D printing enabled casting was adapted to overcome the restrictions on traditional machining processes, we presented a fabrication method for complex injection molding mold pieces with a shorter time and lower processing cost than traditional machining and laser-or e-beam-based 3D printing methods. Based on the plastic injection molding simulation results, which considered the cooling rate of the contact lens mold and the cooling time of each part of the mold, we concluded that the design of conformal cooling channel locating at contact lens mold had little influence on the period of injection. When the mold cavities had smaller total volume ratio than the sprue, such as our contact lens mold, the cooling time of the sprue would be longer than the mold cavities, therefore more attention should be paid on the cooling of the sprue. However, the simulation results showed that the cooling efficiency did not increased significantly when a conformal cooling channel was placed in the sprue bush. But the cooling time reduce about 20%. In other words, the cooling of sprue bush dominated production cycle time. Therefore, a smart mold with real-time temperature monitoring was made with 3DP and mold flow simulation for this work.