AbstractDifferent molecular weight fractions of lignosulfonates (LS), LS having different cations, and modified LS with different degree of sulfonation and intrinsic viscosity were prepared and used as dispersants for Dimethomorph water-dispersible granules (DWG). The suspending ratio of DWG was tested to evaluate the effectiveness of LS as a dispersant. Moreover, the stability of DWG suspensions was measured by a new instrument (Turbiscan LabExpert). The suspending ratios of DWG having different molecular weight fraction of LS increased with increasing molecular weight in a suitable range. The kind of cation associated with the LS didn’t have an obvious influence the effectiveness of LS as a dispersant. Furthermore, the higher degree of sulfonation of LS, of which the intrinsic viscosity was similar, the better was its effectiveness as a dispersant. When the intrinsic viscosity increased within a suitable range, the effectiveness of LS as a dispersant increased. Similar findings were achieved by evaluating the stability of DWG suspensions with all the LS as dispersants, and larger molecular weight could decrease the growth of particle size.