Lignosulfonates obtained from pulping spent liquor are nontoxic and renewable polymers with excellent dispersibility as disperse dye dispersants. In order to reveal its dispersion mechanism on the dye, the adsorption characteristics of sodium lignosulfonate (NaLS) and sodium naphthalenesulfonic acid formaldehyde (NSF) were investigated using a quartz crystal microbalance with dissipation (QCM-D) and an atomic force microscope (AFM). The results showed that the adsorption of dispersant onto the dye film layer was low and unstable without salt, but the adsorption amount of NaSL or NSF onto dye film was increased significantly with the increase in ionic strength. This indicated that hydrophobic effect was the main interaction between dispersant and dye. The adsorption amounts of both dispersants were decreased with the increase in temperature. NaLS exhibited the better dispersion and improved stability at high temperature than NSF due to higher adsorption amount and the viscoelastic adsorption layer.