The invention belongs to the field of thermal plastic molding, and in particular relates to a stirring and heating device of a plastic extruder. The stirring and heating device of the plastic extruder comprises a power device, a bearing assembly, a stirring device, a heating device, a conveying heating barrel, temperature sensors and a control display, wherein the power device is arranged in the front part of the conveying heating barrel and is connected with the stirring device through the bearing assembly; the stirring device comprises a stirring shaft and a threaded structure; the stirring shaft is of a hollow structure and is provided with a steam leading-in device and a condensed water leading-out device; the threaded structure is arranged by using the stirring shaft as the axis; the stirring device is arranged in the conveying heating barrel; the heating device wraps the conveying heating barrel; the temperature sensors are arranged at the middle and the tail of the conveying heating barrel; the control display is arranged on the power device. The stirring and heating device of the plastic extruder has the beneficial effects that the structure is simple, and the design is reasonable; uniform heating and forward conveying can be realized by virtue of the stirring device in the conveying heating barrel; the stirring and heating device has a heating function, so that the heat transfer area can be increased, the heat exchange efficiency is improved, and the mixing speed, melting speed and conveying speed of raw materials in the conveying heating barrel are increased.