Abstract: The method using effective components of naphthalene oil to synthesize the additive for coal water slurry (CWS) was studied. Through proper experimental design and multianalysis of linear regress, the optimum synthesis conditions were obtained. That is, 30 mL H2SO4 was added into naphthalene oil (75 g) to initiate a sulfonation reaction at 160 ℃ for about 2 h. After hydrolysis, 25 mL HCHO was put into the reactor to cause a condensation reaction at 105 ℃ for 1.5 h. Experiments of CWS preparation with the additive synthesized and with the pure naphthalenesulfonic acid formaldehyde condensation product indicate that the additive synthesized has good dispersive property and low cost. The functional groups of the present additive are investigated by Fourier Transform Infrared Spectroscopy (FTIR), which indicates that the additive contains some aromatic compounds with －CH2－，－SO3－functional groups. Finally, the mechanism for improving the property of CWS by the additive is probed preliminarily.