The telescopic chute adopts double casing structure, which is composed of chute and dust cover. The material passes through the chute, and the dust cover is covered on the chute. During the process, the dust suction chamber is moved. The bottom of dust-free telescopic chute will be provided with material level sensor and dust-proof group cover. The material level sensor will be set on the outside or inside, and the dust cover will be of block overlap type. In the loading process, after the material level sensor contacts the material, the dust-free telescopic chute will be lifted in time to keep a certain distance between the material top and the accumulated materials. The dust-proof group cover can cover the material pile to ensure the dust collection effect and prevent dust overflow. The chute will be made of steel plate with polyurethane wear-resistant lining plate, and the dust cover is made of chemical fiber material with anti-static soft strength. A supporting framework will be set in the dust cover, which can not only stretch up and down, but also ensure smooth air flow. At least three lifting points will be set at the bottom of the telescopic chute to ensure that the lifting mechanism drives the telescopic chute to rise and fall smoothly.