The utility model provides a blockage detecting and alarming system of an impurity removing machine. The system comprises a first leather conveyor, a second leather conveyor, a third leather conveyor,an impurity removing machine, a first detection photoelectric tube, a second detection photoelectric tube, an alarm and an electric control system, firstly, a first detection photoelectric tube on afirst leather conveying machine detects whether materials are normally conveyed or not; conveying the materials to an impurity removing machine; a second detection photoelectric tube on the second leather conveyor is used for detecting whether materials are output to the second leather conveyor or not through the impurity removing machine; if no material is detected, it means that the impurity removal machine is blocked, the electric control system controls the first leather conveyor to change the conveying direction according to a signal sent by the second detection photoelectric tube, and the third leather conveyor directly outputs the material which is not subjected to impurity removal, so that the situation of material interruption is avoided, and the situation that the impurity removal machine is blocked is found in time and quickly.