The three-dimensional (3D) dynamics of a propane diffusion flame was investigated using high speed stereo imaging and a newly developed stereoscopic schlieren techniques. The laminar flame is kept at a flow rate of 0.3 slpm, which corresponds to a mean exit flow velocity of 0.30 m/s and a low Reynolds number at 300. The flame shows a typical flickering phenomenon at 11 Hz. The 3D dynamics of the visible flame and invisible hot gas bulge in an oscillating cycle is analyzed quantitatively. The 2D dynamics of the flame and hot gas was investigated based on direct and schlieren images. The in-depth information was obtained by stereoscopic technique and 3D reconstruction methods. It is found that both the visible flame and hot gas bulge has a rotating trend in space, which indicates that the visible flame dynamics is closely related to the hot gas outside. The successful application of 3D schlieren method on flame dynamics shows great potential in future combustion research. (C) 2013 Elsevier Ltd. All rights reserved.