In　order　to　find　a　biological　phosphorus　removal　enrichment　method　with　high　performance　and　low　energy　consumption,　two　enrichment　methods　were　used　in　this　study,　namely　gradient　carbon　source　addition　(S1)　and　fixed　carbon　source　addition　(S2).　The　two　enrichment　methods　were　applied　to　the　enrichment　of　phosphorus　removing　bacteria　in　an　independent　biological　phosphorus　removal　system　based　on　nitrogen　removal　by　immobilized　fillers.　The　phosphorus　removal　performance,　stoichiometry　and　microbial　structure　were　compared　for　the　two　enrichment　methods.　It　was　found　that　PO43--P　remained　0.15-0.2　mg/L　at　the　end　of　enrichment　in　S1,　while　PO43--P　increased　from　0.27　to　0.38　mg/L　at　the　end　of　enrichment　in　S2.　Stoichiometric　analysis　showed　that　S1　used　more　PHAs　(1.47　molC/L)　for　phosphorus　absorption,　while　S2　used　nearly　half　of　the　PHAs　(0.87　molC/L)　for　glycogen　synthesis.　Moreover,　the　absorbed　phosphorus　content　in　S2　was　significantly　less　than　S1　(5.67　＜　8.65　mg/L).　As　a　result,　denitrifying　phosphorus-removing　bacteria　predominated　S1,　while　phosphate-accumulating　organisms　(PAOs)　and　glycogen-accumulating　organisms　(GAOs)　both　played　a　role　in　S2.　Dechloromonas,　the　dominant　denitrifying　PAO　in　both　S1　and　S2　increased　from　0.26　%　to　3.34　%　and　1.04　%,　respectively,　while　Defluviicoccus,　a　typical　GAO,　changed　from　0.24　%　to　0.2　%　and　2.01　%,　respectively.　As　a　result,　gradient　carbon　source　enrichment　demonstrated　a　better　phosphorus　removal　effect　and　dominant　bacteria,　whereas　the　fixed　carbon　source　enrichment　increased　the　abundance　of　GAOs　while　negatively　impacting　the　phosphorus　removal　effect.