The invention discloses a hydraulic power mechanism telescopic device. The hydraulic power mechanism telescopic device is characterized by comprising a plunger, oil inlet holes, a cylinder barrel, a guide ring, a shaft seal and a dustproof ring, wherein the cylinder barrel and the plunger are comprised, the cylinder barrel sleeves the plunger, the dustproof ring, the shaft seal and the guide ringare installed between the cylinder barrel and the plunger, and one oil inlet hole is formed in each of the two sides of the cylinder barrel. The hydraulic power mechanism telescopic device has the advantages that the rotation of the plunger in movement can be controlled so that the plunger can be accurately in butt joint with a butt joint object, the structure is simple, the design is reasonable,the production cost is low, and the sealing and dustproof effects are good.