Abstract: The simulated samples of coal gasification blackwater are made up of fine slags of entrained-bed coal gasifi- cation and the ultrapure water. The flocculation of the fine slags is investigated with certain industrial flocculants. The effects of the amount of flocculant,pH value of the samples,flocculanting time,and stirring time are studied. The ther- mo-stage microscope is used to observe the flocculation of fine slags in simulated samples. The fractal theory was intro- duced to analyze the flocs images of flocculation process. The results show that the fractal dimension of the floc and the concentration of suspended solid flocculation negatively correlate,that is,the greater fractal demension,the smaller the concentration of suspended solids after flocculation. The fractal dimension of the flocs with flocculation time increases first and then decreases. There is the exponential relation for both the number of flocs fractal dimension and floc angle. The fractal dimensions of the floc increase with the increasing angle. Therefore fractal dimension of the flocs can be used for the study of flocculation.