Abstract: Zeta potential method was used to select wetting dispersant in preparing 20% diflufenican suspension concentrate,the average particle diameter(D_av) of test system was determined using a laser particle distribution instrument. The results show that all test anionic wetting dispersants, beside sodium lignosulfonate,could make the suspension particle to reach the absolute value of Zeta potential (|ζ|) in excess of 40 mV, and the suspension concentrate was comparatively stable. When mixed anionic wetting dispersants (NNO and Morwet D425) were used instead of single NNO or Morwet D425,|ζ|of the suspension system was higher than that of single system at the same usage amount. When m(NNO):m(Morwet D425)=1:4, and mass fraction of the mixture was 1%,|ζ|could reach the maximum and the average particle diameter of the system was the smallest. The changes of|ζ|and D_av were very small after heat storage treatment, and the corresponding system achieved the best dispersion effect. Thus zeta potential value of the suspension concentrate has a good correlation to the average particle diameter. Therefore the dispersing effect of wetting dispersant in suspension concentrate could be well represented by the zeta potential value.