A device for preparation of composite for on-site pipeline reinforcement includes: a temperature control stirring unit, an infiltration unit, and a vacuum unit communicated in sequence, the infiltration unit includes a spindle, reinforced fiber cloth, a flow-guiding net, and a vacuum bag film sleeved outside them, the spindle is stopped by two baffles, an adhesive feeding joint and an adhesive discharging joint are disposed at two ends of the spindle, respectively, the adhesive feeding joint and the adhesive discharging joint each includes an inner joint and an outer joint, sealing discs disposed at a junction between the inner joint and the outer joint, an outer wall of the inner joint and an outer side of the baffle are covered by a flow-leading net, and the flow-guiding net covered on the outer side of the baffle extends from an edge of the baffle into the adhesive storing compartment of the baffle.