The utility model provides a sieving mechanism before glass tempering, its characterized in that: it includes be equipped with last piece roll table in the frame, is equipped with the microwave radiation system in the frame of last piece roll table one side, is equipped with detecting system in the frame of microwave radiation system one side. The utility model has the advantages of simple structure, convenient operation, especially detect glass before the glass tempering, the glass board that will contain the nickel pyrite tiny particle is rejected, has saved the homogenization treatment behind the tempering, has practiced thrift the energy, has improved the tempering yield.