The invention discloses a production process of circular arc-shaped plastic profiles. The production process comprises the steps of dissolving thermoplastic particles through a thermoplastic extruder,conducting molding and extruding through a special mold, extruding a thermoplastic material with the molded cross section, feeding the thermoplastic material into a cooling tank, sawing off thermoplastic fenders through an electric saw after extrusion and manufacturing the fenders with the required curvature. Compared with the prior art, the production process has the advantages that the stayingtime of the thermoplastic material in the mold is shortened through the extrusion molding process, and the material is prevented from yellowing; through the extrusion molding process, ejector pin marks cannot appear on the plastic fenders, and the surfaces of products are more smooth; while the material is cooled, the curvature of the fenders is adjusted through an adjusting mechanism; the fenderswith different curvatures can be manufactured through the same mold and the same machine to adapt to different bicycles, the number of molds to be manufactured is reduced, the cost is reduced, and the production process is friendlier to environment. Through the production process, the diameter range of the curvature can be adjusted within 40 mm-85 mm.