In this paper heat transfer through argon gas between two stationary walls of a nano sized channel, is investigated by the use of molecular dynamic method. Comparison between two and three-dimensional solutions shows that for accurate modeling of wall force filed on heat transfer, the accuracy of two-dimensional molecular dynamic solution is inadequate. Two-dimensional solution predicts the value for density and temperature less than the value of three-dimensional solution near each wall. Considering the effect of domain size on accuracy of thermal solution shows that domain size should be extended at least for one mean free path in periodic direction to have domain independent results. Distribution of fluid properties in the width of the channel shows that independent of implemented temperature difference, presence of the wall force field changes the temperature and density profile in one nanometer from each wall drastically. In addition to variation in density due to the wall force filed, temperature difference between the walls cause additional variation in density profile near walls. Increasing the temperature difference between the walls to value more than 20 degree, make a notable density variation to more than 5 percent in comparison with gas density distribution in isothermal walls case. Variation in density near walls due to temperature differences leads to mismatch between the non-dimensional temperature profiles and calculated thermal conductivity coefficient of the gas for various temperature differences.