Gears as main components for the function of motion and power transfer play very important roles in mechanical equipment. Compared with metal gear, plastic gear has many advantages, such as lightweight, low noise, good wear resistance, good self-lubrication performance, corrosion resistance, and it has the characteristics of easy molding, low manufacturing cost, and flexible design, etc. Compared with the traditional forming and manufacturing methods for metal gear, the forming and manufacturing methods for plastic gear are very different due to the significant difference in the types and properties of plastic materials. Referring to relevant literature on plastic gears, the characteristics, properties, and applications of different plastic gears were summarized, and the main manufacturing methods of plastic gears including injection molding, 3D printing, and machining were analyzed.