Abstract: Following an introduction on the testing principle,instrument and equipment,and field signal acquisition process for method of additive mass, this paper deals briefly with its availability on the density measurement of rock-fill object in the Shubuya Dam One Issue Project. The testing results indicate that this method not only has rapid, portable, non-destructive, and precision high, but also suitable for density measurement of rock-fill object made up of different grains. It is proved that method of additive mass is obviously effective and hence shows fairly good application prospects in the density measurement of rock-fill object.