Foam dust suppression is an efficient method to control dust hazards, in which the foam morphology is closely related to its dust-suppression performance. As a commonly used foaming agent auxiliary, water-soluble polymer (e.g. carboxymethyl cellulose) is believed to be able to change foam morphology. To explore the effect of carboxymethyl cellulose (CMC) on the foam morphological characteristics, CMC was added in alpha-olefin sulfonate (AOS) solution at different concentrations and tested for the influence on bubble size, distribution and uniformity of AOS foams. The results showed that both during the foam formation and decay, the average bubble size decreased, and the foam uniformity simultaneously increased with an increase of AOS concentration, and furthermore, the size and uniformity gradually stabilized when the AOS concentration was higher than 0.1 %. After CMC addition, there is an optimal turning point (0.1 % AOS) where the effect of 800 mg/L CMC addition on foam morphology is most pronounced, the average radius of bubbles could reach a minimum of 0.13 mm, and the uniformity reaches the highest. Adding CMC of 800 mg/L in 0.1 % AOS solution is an effective way to optimize the morphology of dust-suppression foam. This study provides important reference for using water-soluble polymer to improve the performance of dust-suppression foam in engineering. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.