Experiments have been conducted to investigate nitrogen gas flow characteristics through four trapezoidal sili-con microchannels with different hydraulic diameters. The volume flow rate and pressure ratio are measured in theexperiments. It is found that the friction coefficient is no longer a constant, which is different from the conventionaltheory. The characteristics are first explained by the theoretical analysis. A simplified rectangular model (rectangularstraight channel model) is then proposed. The experimental results are compared with the theoretical predictions basedon the simplified rectangular model and the two-dimensional flow between the parallel-plate model which was usuallyuse The difference between the experimental data and the theoretical predictions is found in the high-pressure ratiocasesx. The influence of the gas compressibility effect based on the Boltzmann gas kinetic analysis method is studiedto interpret the discrepancy. We discuss two important factors affecting the application extent of different predictionmodels.