Gears have been used as a means of power transmission for a long time as a part of various mechanical devices. In the past, gears made of matal have been mainly used, but now the use of polymer gears is increasing. Polymer gears are lighter in weight than metal gears, have superior operating performance, generate less noise and vibrations, and can be driving no-lubrication, which has numerous mechanical and environmental advantages over metal gears. However, polymer gears have disadvantages in that they have weak mechanical properties and are very weak to heat. Also, polymer gears tend to be easily fractured by frictional heat due to their low thermal conductivity. For this reason, polymer gears are not applied to heavy machine such as automobiles or aircraft, but are used in light-load machine such as office equipment or home appliances. Therefore, there is a need for research to improve the reliability of polymer gears for application to a wide range of industries. The goal of this study is to improve the reliability of polymer gears through tooth shape modification and surface treatment. In this study, a gear was manufactured using 3D printing, and the driving characteristics of the gear according to the tooth shape of the polymer gear were analyzed. And the tribology characteristics according to various materials and surface treatment were analyzed, and the material and surface treatment with the best tribology characterustucs were applied to the polymer gear. The tooth shape design of polymer gears was analyzed for involute gear and cycloid gear, which had not been studies in the polymer gear. Tribology characterization was tested on ABS, PE, PP, and PA materials, and the surface was treated with surface chemical polishing and CNT coating. As a result of the experiment, the cycloid tooth reduced frictional heat by up to 32% compared to the involute tooth. And the efficiency was also the best with the cycloid tooth shape. The material and surface treatment with the best tribology properties are those that are PA material and surface chemical polishing and CNT coating. In a comparison experiment with typical gears, the gears manufactured through this study(Cycloid tooth shape PA material, surface chemical polishing and surface CNT coating) reduced frictional heat by up to 70%, and the wear rate by 60%, and the efficiency increased by up to 10%. This study showed that cycloidal teeth of polymer gears have better operating performance than involute teeth. And materials with good tribological properties also have good gear operating performance, which can be further improved through surface treatment such as surface polishing or CNT coating.