The average density of particulate grain pile is an important parameter for real-time online measurement of grain stock quantity. In order to solve the problem of calculating the average density of particulate grain pile in the inventory of grain processing enterprises, a calculation method for the average density of particulate grain pile in silos was proposed based on the comparison and analysis of the existing methods. Besides, a complete process of grain filling and discharging o f a rice silo was selected to verify the measurement accuracy and practicability of the method. The results shows the method meet the requirements of use. This method is simple, practical, and accurate. In addition, the method overcomes the shortcomings of the existing correction coefficient method and provides technical means for dynamic inventory count in grain processing enterprises.