The invention relates to a low-cost and high-efficiency machining method for cycloid gears. The method is characterized by comprising the following process steps that (1) round metal billets are selected as raw materials; (2) the round billets are subjected to normalizing treatment; (3) the round billets are subjected to gear broaching; (4) the billets are subjected to phosphating and saponifying treatment in sequence; (5) the billets are subjected to oil film lubrication and extrusion machining; (6) annealing is carried out; (7) the step (4) and (5) are repeated; (8) auxiliary holes of the billets are machined with a cycloid as the benchmark; (9) quenching treatment is carried out; (10) tempering treatment is carried out; (11) workpieces are subjected to finishing machining; and (12) polishing treatment is carried out. According to the method, the cycloid gears are subjected to extrusion machining for two times through the oil film lubrication and extrusion technology; the cycloid gears are subjected to polishing treatment through abrasive flow machining technology; the machined cycloid gears are low in surface roughness and high in dimensional accuracy; and the machining efficiency of the cycloid gears is remarkably improved, and the machining cost is reduced.