Abstract: Pressure swing adsorption is the feasible method for nitrogen and methane separation in the oilfield associated gas. The adsorption isotherm of nitrogen and methane on the activated carbon WHXR-LB20 were determined by gravimetric method. The separation coefficient was 2.87, which could satisfy the demand in industrial application. The activated carbon had good regeneration effect to nitrogen and methane. The effects of ethane, propane and n-butane in the oilfield associated gas on WHXR-LB20 were determined. The results showed that the activated carbon has good regeneration effect to the ethane and propane. But the n-butane accumulated on the WHXR-LB20. The accumulation amount reduced the saturated adsorption capacity of nitrogen and methane on the activated carbon WHXR-LB20.