Experiments of nano-scale polymethylmethacrylate dust explosions were conducted to reveal the flame propagation characteristics and evolution mechanism. The results showed that the flame preheat zone front was approximately smooth. The average pulsating flame propagation velocity and maximum temperature both increased with an increase in dust concentration. The thermal heat transfer rate and pyrolysis rate dominated the propagating flame. A transition from pyrolysis rate control to combustion reaction rate control occurred as the dust concentration increased during the combustion process. Speculating from the physical model of nano dust flame propagation including a post-flame zone, a luminous spot-flame reaction zone, a combustible premixed-gas reaction zone, a preheat zone, an unburnt particle stagnation zone, and an unburnt zone away from the flame front, the propagating flame was macroscopically analogous to the kinetic combustion of premixed gas. In addition, it was microscopically coupled with the localised diffusion combustion of luminous spot flames. (c) 2019 Elsevier B.V. All rights reserved.