Series　of　studies　of　adsorbent　in　the　enrichment　and　separation　of　coal　mine　gas　were　carried　out,　five　kinds　of　ACFs　were　chosen　and　their　BET　surface　area　and　adsorption　isotherms　of　CH4　and　N2　at　298　K　were　measured.　By　comparing　adsorption　capacities　and　separation　factors,　an　optimal　adsorbent　chosen　and　modified　with　ammonia　to　explore　the　best　modification　conditions.　Results　show　that　ZC1　is　the　best　adsorbent.　It　is　shown　that,　in　comparison　with　the　original　ACF,　the　modified　ACFs　have　larger　pore　volume　and　larger　surface　area,　so　that　their　adsorption　capacities　of　CH4　and　N2　are　the　highest.　The　ACF　modified　with　5　mol/L　ammonia　aqueous　solution　is　the　best　one　and　its　separation　factor　reaches　5.32.