The fluid flow and heat transfer characteristics of rectangular, triangular and trapezoidal micro-channels are analyzed. The influence of height-width radio and channel types on these characteristics is simulated. The results show that the coefficient of friction resistance decreases with the increase of Reynolds number but increases with the rise of aspect ratio in micro-channels. At the same Reynolds number and aspect ratio, the maximal coefficient of friction resistance appears in the rectangular structure, and the minimal one in the triangular micro-channel. When the channel type and the aspect ratio are fixed, the Nusselt number increases with the Reynolds number, but the increasing trend is slow. General empirical formulas are proposed to evaluate the heat transfer performance of different micro-channels with consideration of inlet effect and height-width ratio.