This paper investigates the effects of the EDL at the solid-liquid interface on Liquid flow and heat transfer through a microchannel between two parallel plates at constant and equal temperatures. A linear approximate solution of the Poisson-Boltzmann equation is used to describe the EDL field near the solid-liquid interface. The electrical body force resulting from the double layer field is considered in the equation of motion. The equation of motion is solved for the steady slate flow. Effects of the EDL held and the channel size on the velocity distribution, streaming potential, apparent viscosity, temperature distribution and heat transfer coefficient are discussed in this paper.