Characteristics of coal- water slurry( CWS) and conventional dispersants for its preparation were introduced. Factors that affect the preparation of highly concentrated CWS and mechanism for action of the dispersant on the pulverized coal were described. Influence and principle of molecular structure of different dispersants on performance of the CWS were emphatically summarized. In addition,model for possible molecular structure of a perfect dispersant as well as the way for its synthesis was proposed.