The flow and heat transfer of rarefied gas in rough microchannels, which are confined between two infinite large parallel plates with uniformly distributed triangular rough elements, are simulated by DSMC method with Delaunay triangulation meshes. Analysis and comparison are carried out on smooth and rough channels with rough elements of different size or/and distribution density. Roughness in micro-channels affect the gas flow and heat transfer greatly. As the size or/and the number of rough elements increases, the gas velocity jumps more seriously, even being accompanied by some vortices; furthermore, the gas temperature increases, but both the mass flux and the heat transfer rate decrease. In the flow direction, the gas temperature rises first and then falls; the local pressure increases at the windward of rough elements and decreases at the leeward side; moreover, the heat flux at the surface shows violent fluctuation, that is, the heat flux at the rough element surface is much smaller than that at the channel wall surface.

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