The distance measures of similarity between vague sets (values) have been developed to solve the problem of slagging characteristic of coal ash, and a slag-prediction model of coal ash based on vague sets was proposed. In the model, four single indices and their bounds are involved. The indices are ST, SiO2/Al2O3, B/A and G. At the same time, 25 coal ashes were selected as samples. the model was employed to predict the slagging characteristic of the 10 coal ashes. Through predicting, determining and comparison, it proved that the accuracy of the pattern recognition model was 90 percent and met the engineering requirements. So the model built was reasonable and feasible.
