The authors investigate the component fabrication of a flapping ornithopter with 21.6 cm wing span by using precision injection molding. For making a bio-mimicking flapper like birds, two fold of plastic injection moldings have been done. Firstly the flapping mechanism of a 4-bar linkage gear transmission module has been studied, and the according plastic components for the gear transmission module were designed as light as possible. Thereafter the injection flow analysis in the multi-mold cavity and the fabrication parameters of the molding process has been implemented.The finished polyoxymethylene (POM) components for the transmission module of 1.2 gram in mass finally verify the design and process of the precision injection molding. After the ornithopter Golden Snitch was assembled and tested with the fore-mentioned plastic 4-bar linkage, a maximum flight record of 480 sec was created in 2010. The second framework of injection molding is to design a bird-like expandable polystyrene (EPS) fuselage with 19.5 cm in length as the mechanical protection. After this ornithopter Golden Snitch-Pro was assembled, it has a successful flight of 230 sec and 100 times of landing capability. In summary, the fabrication of a polymeric bird-like flapper is proved, and the precision injection molding technique shows its feasibility in realization of ornithopters.