Cyclic gas injection is considered as an effective and quick responding recovery process to enhance the shale oil recovery compared with water or gas flooding. And many finished lab experiments using Carbon dioxide and Nitrogen cyclic injection with core samples have proved its effectiveness. The impacts of oil saturation time, soaking time, depletion time, injection pressure, and cycle numbers have been tested in our previous work. However, the influence of core size on oil recovery is a very important parameter when upscale the core size to field level. Also, methane is a more economic and convenient gas source when considering the injection cost compared with carbon dioxide. In order to get the more accurate and reliable results, cyclic methane injection were used and the cores from Eagle Ford with different diameters (1 inch, 2 inches, 2.5 inches, 3 inches, 3.5 inches and 4 inches) were saturated with crude oil from Wolfcamp in this experiment. A numerical model was built using the typical reservoir properties from Eagle Ford to simulate cyclic methane injection. Sensitivity analysis, history matching and size upscale are conducted. The experiment results show that oil recovery factor decreases with the incremental of core sizes from 1 to 4 inches. Simulation results show that the most important parameter is injection pressure followed by matrix permeability, porosity and methane diffusivity. When upscale the core size to field level, the oil recovery decreased.