A model of mini heat sink with microchannels was developed to obtain homogeneous heat transfer capability. The channels are constructed in the form of eight triangular arrays based on a square substrate. Air is sucked from the periphery to the center of the substrate by a vacuum pump and heat transferred from the bottom surface of substrate can be removed by air flowing through channels. Corresponding to the given heat transfer power and the target temperature of substrate, the relationship among length, width and depth of channel was analytically established. By numerical simulation, local pressure drops at the joint of channels and air duct are first obtained and then the dimensions of each channel in a triangular array can be determined one by one. The investigation reveals that the widths of channels will vary with their depths, lengths and pressure differences between two ends. Since all channels are required for the same cooling power, the homogeneous heat transfer of heat sink can be realized. By assembling a certain number of heat sink units, the area of dissipation of heat sink can be enlarged and contoured to fit close to heating surface.