The present invention provides a method for fast evaluating dispersibility of gasification ash water 
dirt dispersion agent. The method comprises the following steps: A) allocating a grain 
diameter ofcoal ash, so that grain 
diameter distribution of the 
coal ash matches grain 
diameter distribution of fine ash in gasification ash water; B) mixing the 
coal ash with water, to obtain suspension liquid,heating the suspension liquid in water bath, and then performing stirring, to obtain experimental suspension liquid; C) keeping the experimental suspension liquid static, and testing blank 
turbidity;D) repeating steps A) and B), and then adding a 
dirt dispersion agent to the experimental suspension liquid obtained in step B), keeping static and testing 
turbidity; and E) calculating a dispersionratio M of the 
dirt dispersion agent. According to the evaluation method, working conditions of a factory gasification black water 
system are restored to a great extent through technologies such as constant temperature and allocating 
coal ash grain diameter. The method is simple and intuitive to operate and strong in feasibility; fills the gap that dispersibility of the dirt dispersion agent usedby a 
coal gasification slag sluicing 
system can be evaluated, and has guiding significance for factory chemicals selection.