The invention discloses a dustproof telescopic discharge pipe for a belt conveyer. The dustproof telescopic discharge pipe is characterized in that a head funnel, a telescopic discharge pipe and a dustproof curtain which are connected through bolts are sequentially arranged in the discharge direction; multiple pulleys are uniformly fixed to the outer side wall of the first-section discharge pipe close to the head funnel; steel wire ropes are arranged on the pulleys; one ends of the steel wire ropes are connected with a rotating shaft of a stepping motor; the other ends of the steel wire ropes are connected with lifting lugs arranged on the tail-section discharge pipe; a sensor used for detecting the height of materials is arranged on the tail-section discharge pipe; the dustproof curtain is fixed to the bottom of the tail-section discharge pipe; the sensor and the stepping motor are connected with a single chip microcomputer controller through a circuit; and the single chip microcomputer controller is connected with a power source through the circuit. According to the dustproof telescopic discharge pipe, the problem that the environment is polluted by flying dust generated when a conventional belt conveyer conveys powdery materials is solved, and the environment is prevented from being polluted through utilization of the discharge pipe which can be stretched and retracted according to materials.