There are abundant metallic mineral resources on the sea floor, polymetallic nodule is an important one of them. A polymetallic nodule ore includes nickel, copper and manganese elements, etc. So the polymetallic nodule is very important and precious to industry. In order to know the distribution and reserves in the west and east pacific areas, a deep-tow optic system is imported from U.S. to acquire deep sea-floor images. Processing the images, we can extract some information and calculate some parameters: coverage, grain size and abundance, which stand for distribution and reserves of the polymetallic nodule. In the paper, features of the deep sea-floor image are analyzed, considering the characters, a processing procedure for the deep sea-floor pictures is presented. Methods are presented to rectify radiative uneven and geometric distortions, at last, the correlations of coverage, abundance and grain size are analyzed and the formulas for computing abundance are respectively derived from that.