The invention belongs to the technical field of composite part manufacturing, particularly relates to a composite pipe part demoulding method. The composite pipe part demoulding method comprises the following steps: a, first placing a tubular vacuum bag (3) on a male die (2); b, premolding a part (4); c, combining a female die (1) of an upper and lower die structure onto the male die (2) paved with the part, the upper and lower die are locked and sealed; d, adhesively sealing the tubular vacuum bag (3) on the female die (1) by two side edges of the part so as to form a sealed space among the female die (1), the tubular vacuum bag (3) and the part (4); e, extracting out air in the sealed space formed in the step d, compacting the part (4) in the female die (1) so as to form a gap between the part and the male die (2); and f, extracting out the male die (2) from the part (4). The composite pipe part demoulding method improves the part manufacturing quality, improves the manufacturing efficiency, and reduces the manufacturing cost.