To　promote　the　application　of　nitritation　in　actual　domestic　wastewater　treatment,　stable　partial　nitritation　(PN)　in　a　moving　bed　biofilm　reactor　treating　low　strength　wastewater　at　low　temperature　(15　degrees　C,　12　degrees　C　and　8　degrees　C)　was　successfully　achieved　under　high　dissolved　oxygen　(DO)　concentration　through　ratio　control　which　was　the　ratio　of　DO　and　total　ammonia　nitrogen　(TAN).　The　mechanism　of　achieving　nitritation　through　ratio　control　and　the　effect　of　organic　carbon　contained　in　wastewater　on　achieving　stable　PN　at　temperature　of　8　degrees　C　were　investigated.　Results　indicated　that　at　temperature　of　12　degrees　C　stable　nitritation　could　be　achieved　through　controlling　ratio　not　exceeding　0.16　exerting　effective　repression　on　NOB　populations　which　would　be　washed　out　slowly.　Organic　carbon　is　largely　beneficial　to　achievement　of　stable　PN　at　temperature　of　8　degrees　C,　resulting　in　looser　oxygen-limited　conditions　(DO/TAN:　0.2)　than　that　(DO/TAN:　0.16)　at　temperature　of　12　degrees　C.　But　not　the　more　organic　carbon　the　better　nitritation　performance,　an　equal　number　of　COD　(C/N　=　1)　should　be　adequate.　In　practical　applications,　to　achieve　stable　PN　for　actual　mainstream　under　high　DO　concentration　at　temperature　not　lower　than　8　degrees　C,　TAN-dominated　ratio　control　should　be　a　suitable　control　strategy.