The objective of this research is to evaluate optimal conditions of permeability and selectivity on the polysulfone membrane for efficiency of separation of CH4 by checking four factors which are temperature, pressure, gas compositions and gas flow rates. When higher pressure was applied at the input, lower efficiency of recovery of CH4 and higher efficiency of separation of CH4 were shown. It has the tendency to show lower efficiency of recovery of CH4 and higher efficiency of separation of CH4 at the output as higher temperature at input. The lower flow rates make higher efficiency of recovery of CH4 and lower efficiency of separation of CH4. Finally, over 90% efficiency for CH4 separation and recovery conditions are temperature (-5℃), pressure (8 bar), gas composition rate (6:4) (CH4:CO2) and gas flow rate (5 ℓ/min). These conditions make higher separation and recovery efficiency such as 90.1% and 92.1%, respectively.