Abstract: In this paper the covering power of the positive and negative images was determined. It was found that the covering power of the positive image is 3-10 times higher than that of the negative. It was found that the more the silver deposited, the lower the covering power will be on the same positive. And the covering power is seen to depend greatly on the density. With increasing density, the covering power diminishes exponentially. The experimental results showed that any change of the physical development nuclei or nuclei carriers (different kinds of hydrophilic silica) in the positive receiving layer will affect the covering power of the final image, and that the smaller the particle size of deposited silver, the higher the covering power.