Here,　nitrogen　conversion,　granular　characteristics　and　microbial　dynamics　were　combined　to　reveal　the　longitudinal　heterogeneity　along　anammox-UASB　with　nitrogen　removal　efficiency　of　92.6%.　The　reactor　was　divided　into　Bottom-zone,　Middle-zone,　Upper-zone,　and　Top-zone　with　height　increasing.　Results　indicated　that　particle　size　decreased　from　Bottom-zone　to　Upper-zone,　while　granular　floatation　caused　an　increase　in　Top-zone.　Protein　secondary　structure　in　EPS　was　loose　and　hzsA　transcription　ratio　was　only　4.45%　due　to　the　limited　mass-transfer　and　serious　mineralization　of　ultra-large　granules　in　Bottom-zone.　Smaller　granules　in　Middle-zone　were　more　robust　and　active,　with　compact　tryptophan-　and　aromatic-like　protein　in　EPS　and　23.71%　hzsA　transcription.　Intriguingly,　coexisting　denitrification　survived　on　EPS　and/or　microbial　metabolites　was　observed.　Transcription　of　narG　was　stimulated　with　height　increasing,　resulted　in　performance　improvement　through　combining　partial　denitrification　and　anammox　in　Upper-zone.　The　findings　deciphered　stratification　characteristics　along　the　height-partitioned　anammox-UASB,　and　reveal　cross-feedings　between　denitrification　and　anammox　bacteria.　©　2022　Elsevier　Ltd