Suction type specific gravity de-stoning machine is mainly used in grain processing plant. Separate from wheat, rice and other impurities in the specific gravity than the grain, can also be used to separate some other impurities in the grain. This machine is the use of grain and shoulder stone specific gravity and suspension speed of different physical properties with the help of upward through the gap between the grain particles of the air flow to promote the grains and shoulder stone classification, shoulder stone and other heavy impurities in the lower layer, in the direction of tilted reciprocating movement of the action of the de-stoning sieve plate to the end of the stone movement, floating in the upper layer of the grain in the action of the weight, to the end of the discharge flow, so as to separate the shoulder stone from the grains.