Ash content is a vital indicator for coal flotation performance. Froth plays an important role in determining flotation concentrate grade and there are strong correlations between the concentrate froth and the ash content. Therefore, the research in the correlations is of great importance for further flotation prediction and control. In this paper, flotation experiments were conducted at different frother dosages and froth depths using a flotation column. It was found that there were relations between the ash content, yield and water recovery of the concentrates. Variables of froth property such as the average gray value, the homogeneity, the burst bubble parameters and the height over weir were extracted from video images and were analyzed to explain the flotation results. The connections between the variables and the concentrate ash content were analyzed. (C) 2016 Elsevier Ltd. All rights reserved.