Abstract: An experiment has been carried out concerning the grain (wheat, maize and soybean) gravitational flowing rate through a horizontal hole in order to find out the affecting factors, Thus a flowing rate formula has been derived for the calculation. It was found that the size and the shape of the hole, and the size and the moisture content of the grain affected the grain gravitational flowing rate. But, under a certain condition, the height of grain colummn had only a little effect on the grain gravity flow rate.