Based on image analysis technology， the morphological characteristics of fly ash particle groups were analyzed， and the parameters that can quantify the morphology of particle groups were proposed to be one of the criteria to distinguish the morphology quality of fly ash. The results show that the morphology characteristics of fly ash particle groups can be accurately characterized by the proportion of particle area ratio under different roundness grades， and the S_R>0.8/S_R>0.5 （the ratio of particle surface area of roundness above 0.8 to that above 0.5） can best describe the morphological characteristics of particle groups. When it is at 200 times magnification and above， the S_R>0.8/S_R>0.5 of qualified fly ash can exceed 10%， the fact is significantly different from that non-spherical particle powder.