"Flame-street" refers to the interesting combustion phenomenon that a diffusion flame in a narrow channel is separated into a discrete series of flame segments. Although flame-street has been observed experimentally for more than a decade, numerical simulations of this phenomenon with realistic chemistry and detailed analysis of its thermo-chemical structures have yet to be performed. In this paper, the methane-oxygen diffusion flame-street observed by Misse et al. (2005) [36] in a microchannel was numerically reproduced using a reacting flow solver developed based on the open-source framework OpenFOAM. The main purpose of the present work is to investigate the detailed thermo-chemical structures of diffusion flame-street in the anticipation of a deep understanding of the underlying mechanisms responsible for its formation. Our simulation results show that the presence of discrete flame segments can strongly affect the flow field. In addition, the flame-street was found to consist of a bibrachial leading flame with a long diffusion tail and a much weaker fuel-lean premixed branch, and consecutive downstream "new moon"-like flamelets each with a fuel-lean and a fuel-rich premixed branch. Chemical structures of these flame branches were analyzed by examining critical reactions that contribute significantly to the overall heat release. Finally, the effects of channel wall thermal conditions and species mass diffusion on the formation of the flame-street were investigated. It was found that the flame street could be established only at a moderate level of heat loss to the wall: significantly enhanced or reduced heat losses would result in either a single short edge flame or a long continuous edge flame. Increased mass diffusivity was seen to enhance combustion, elongate the leading flame, and even lead to more flame segments that appeared within the channel, although they may exist in a unsteady mode, being repetitively split, moving downstream and being blown-out/extinguished. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.