The utility model relates to a device suitable for small-size grain cutting and belongs to the field of mechanical manufacturing. The device comprises a base, a knife holder, a cutting knife and a length positioning body, both the knife holder and the length positioning body are fixed on the upper surface of the base, the end face of the rear end of the length positioning body is perpendicular to a grain positioning groove of the knife holder, length between the end face of the rear end of the length positioning body and a cutting knife passing groove of the knife holder is matched with that of a to-be-cut grain, the front end of the cutting knife is connected on one side of the cutting knife passing groove through a pin shaft, and one side of a cutting edge of the cutting knife faces the cutting knife passing groove. The device is simple in structure, light and easy to carry, convenient in operation and economically affordable, product appearance quality and length uniformity are improved remarkably, product yield is increased substantially, and the device meets processing requirements, on small-size grain products, of scientific research and production.