The utility model provides a plastic door-window section bar. The plastic door-window section bar is characterized in that at least three cavities are arranged on the cross-section. Because the quantity of the cavity is increased and the real area of the material part of the section bar cross-section is increased, the strength of the section bar is increased. Compared with the plastic-steel door and window section bar, because a reinforcing steel plate is cancelled and the quantity of the cavity is increased, the heat transfer coefficient of the plastic door-wikndow section bar is decreased to the 1/3 of the plastic-steel door and window section bar. The plastic door-window section bar has the advantages of heat insulation, sound insulation, thermal insulation, energy saving, etc.