Phospholipid　fatty　acid　(PLFA)　analysis,　based　on　modem　biochemical　techniques,　is　widely　used　in　the　research　of　microbial　ecology　nowadays.　This　paper　research　the　principles　and　applications　of　PLFA　on　the　microbial　community　of　biological　aerated　filter,　The　experimental　results　show　that　BAF　has　in　significant　differences　in　microbial　communities　under　different　conditions,　various　types　and　content　of　PLFA　also　are　different;　On　parallel　operation,　PLFA　of　microbial　community　in　BAF　were　significantly　higher　than　in　series,　at　this　point,the　capacity　of　biological　aerated　filter　is　greater　than　the　series　run;　In　run-time　series,　PLFA　content　of　microbial　community　in　the　end　of　biological　aerated　filter　process　is　the　smaller,　the　better　the　treatment　effect;　The　special　value　of　PLFA　characterization　can　be　expressed　specific　microbial　community,　with　the　role　and　direction　of　microorganisms　in　wastewater　treatment,　it　can　infer　the　process　running　and　the　treatment　effect.