The invention discloses a high-flexibility composite tube. The high-flexibility composite tube comprises an inner plastic tube, a reinforced steel tube and an outer plastic tube which are sequentially in sleeve joint, wherein spirally distributed strengthening ribs are arranged on the wall of the reinforced steel tube and protrude toward two sides of the inner surface and the outer surface of the wall of the reinforced steel tube; protrusion peaks on the same side are positioned on the same straight line which is parallel to the central axis of the composite tube; a first hot melt adhesive layer is arranged between the inner plastic tube and the reinforced steel tube; a second hot melt adhesive layer is arranged between the reinforced steel tube and the outer plastic tube; the length direction of the composite tube is used as an axis X, the radial direction of the composite tube is used as an axis Y, the connection line of the protrusion peaks on the adjacent same sides of the strengthening ribs is a quadratic function using y as a dependent variable and x as an independent variable, and the inner plastic tube and the outer plastic tube are both made from crosslinked polyethylene. The high-flexibility composite tube disclosed by the invention is good in pressure resistance and excellent in bending property.