The invention discloses an energy-saving plastic extruder which comprises a material barrel. A threaded rod is arranged in the material barrel and can rotate in the material barrel, heaters are arranged on the periphery of the material barrel, the heaters comprise a plurality of first heaters and a plurality of second heaters, the first heaters and the second heaters are arranged at intervals, and the temperature of the second heaters is lower than that of the first heaters; the threaded rod comprises main threads, auxiliary threads arranged in spaces of the main threads, and the height of the main threads is larger than that of the auxiliary threads. The energy-saving plastic extruder is good in fused plastic stirring and pushing effect, capable of saving energy and environmentally friendly.