There are many attractive features for using CO2 foam injection in Enhanced Oil Recovery (EOR) processes. For understanding CO2 foam rheology in porous media, an experimental study is reported in this paper concerning CO2 film foam flow characteristics in a vertical straight tube. Foam is treated as non-Newtonian fluid and its pseudo-plastic behavior is investigated based on power law constitutive model. It is observed the CO2 film foam flow shows clear shear-thinning behavior, with flow consistency coefficient of K=0.15 and flow behavior index of n=0.48. The apparent viscosity of flowing CO2 film foam is under the shear rate of 50s-1 and under the shear rate of 1000s-1, which are 19 and 3 times higher than the single phase water. It is also found CO2 foam has lower apparent viscosity than the foam with air as the internal gas phase, which is in consistence with experimental observations for lower CO2 foam flow resistance in porous media.