Effects of five low-molecular-weight organic acids,i.e.,acetic acid,citric acid,maleic acid,malic acid,and oxalic acid,on electrokinetic properties of two latosols-Kunming latosol and Xuwen latosol were investigated in this work.The results showed that under the experimental conditions with the increase in the concentration of acetic acid,the potentials of Kunming latosol and Xuwen latosol were gradually shift ing to the positive direction,and then the movement increased in velocity significantly,till the potential leveled off.With the increase in the concentration of citric acid,however,the potentials of Kunming latosol and Xuwen latosol moved towards a further negat ive direction,with the velocities being more or less the same between the two latosols within the range (0~0.15 mmol L^-1) of the tested concentration.With the pH value ranging between 3.2 and 6.0,the potentials of the two latosol suspensions containing different organic acids showed a decreasing order of acetic acid> maleic acid> malic acid> citric acid> oxalic acid;and the potentials of suspensions containing the same organic acid were always higher for Kunming latosol than for Xuwen latosol.In the presence of different organic acids the isoelectric point (IEP) of the two latosols followed the same order as that of potentials mentioned above;and as for the same treatment,IEP of Kunming latosol was 0.5~1.0 pH unit higher as compared with that of Xuwen latosol.