Organic wastewater can be used to prepare coal water slurry (CWS) for the resource utilization of organic wastewater. The components in organic wastewater are highly complex, and some of their substances can influence the properties of CWS. Here, the effects of six metal ions in organic wastewater on the properties of CWS and the interaction mechanism with a dispersant are studied. Findings show that Fe3+ can increase while Cu2+ can decrease the apparent viscosity of slurry, whereas Mg2+, Ca2+, K+, and Na+ have no corresponding obvious effects. The stability of the slurry is improved by adding Fe3+ and Cu2+, whereas those of the other ions have no considerable effects. The inductively coupled plasma optical emission spectrometer, the energy dispersive spectrometer, and the zeta potential are used to analyze the adsorption behavior of metal ions at the coal water interface. Results show that Fe3+ and Cu2+ can adsorb on coal surfaces and change the properties of these coal surfaces, whereas Mg2+ and Ca2+ can hardly adsorb on coal surfaces, which further imply the negligible effects on the properties of the slurry. Furthermore, Fe3+ can form a complex compound with the dispersant, which leads to the inactivation of the dispersant.