1. A footstep telescoping mechanism, comprising main transmission arms (11), secondary transmission arms (12) and lower swing arms (6), wherein the main transmission arms (11), the secondary transmission arms (12), the lower swing arms (6) and fixed seats form four-link hinge structures, the main transmission arms (11) are used for being connected with motors and the main transmission arms (11) are driven by the motors to swing, one end of each lower swing arm (6) is connected with the corresponding fixed seat while the other end is connected with the corresponding lower swing arm (6), the main transmission arms, the secondary transmission arms (12) and the lower swing arms (6) are connected, and the main transmission arms (11) and the secondary transmission arms (12) swing to drive the lower swing arms (6) to swing to extend out or retract; and at least one of the three components of the main transmission arms (11), the secondary transmission arms (12) and the lower swing arms (6) is of the following structure, the structure comprises supporting frameworks (1) which are arranged at inner parts and used as reinforcing pieces, and body pieces (2) which are formed on outer parts of the reinforcing pieces, the body pieces (2) are made of non-metal materials, and the supporting frameworks (1) and the body pieces (2) are cast by a mold to form an integrated structure.