Negative pressure pipe of extruder

The utility model relates to a negative pressure pipe of an extruder, which comprises a pipeline body, a heating belt layer spirally wound on the pipeline body, a heat preservation belt layer spirally wound on the heating belt layer, and at least two hoops tightly sleeved on the heat preservation belt layer, the heating band layer comprises a spiral heating band, a heat insulation cotton strip embedded in a spiral gap of the spiral heating band, and a pair of heat conduction adhesive tapes which are symmetrically arranged on the two sides of the heat insulation cotton strip and fixedly bonded to the two axially adjacent sections of the spiral heating band. The heating belt layer and the heat preservation belt layer are arranged on the pipeline body for heating and heat preservation, the internal environment temperature of the negative pressure pipe can be guaranteed, volatile gas is prevented from being solidified, volatile substances can be promoted to be directly volatilized and sucked away, and the negativ