The　short-term　effects　of　temperature　and　free　ammonia　(FA)　on　ammonium　oxidization　were　investigated　in　this　study　by　operating　several　batch　tests　with　two　different　partial　nitrification　aggregates,　formed　as　either　granules　or　flocs.　The　results　showed　that　the　rate　of　ammonium　oxidation　in　both　cultures　increased　significantly　as　temperature　increased　from　10　to　30　degrees　C.　The　specific　ammonium　oxidation　rate　with　the　granules　was　2-3　times　higher　than　that　with　flocs　at　the　same　temperature.　Nitrification　at　various　FA　concentrations　and　temperatures　combination　exhibited　obvious　inhibition　in　ammonium　oxidation　rate　when　FA　was　90　mg.L-1　and　temperature　dropped　to　10　degrees　C　in　the　two　systems.　However,　the　increase　in　substrate　oxidation　rate　of　ammonia　at　30　degrees　C　was　observed.　The　results　suggested　that　higher　reaction　temperature　was　helpful　to　reduce　the　toxicity　of　FA.　Granules　appeared　to　be　more　tolerant　to　FA　attributed　to　the　much　fraction　of　ammonia　oxidizing　bacteria　(AOB)　and　higher　resistance　to　the　transfer　of　ammonia　into　the　bacterial　aggregates,　whereas　in　the　floc　system,　the　bacteria　distributed　throughout　the　entire　aggregate.　These　results　may　contribute　to　the　applicability　of　the　nitrifying　granules　in　wastewater　treatment　operated　at　high　ammonium　concentration.