Anammox　is　an　advanced　biotechnology　for　nitrogen　removal　and　has　been　widely　applied　in　wastewater　treatment.　Preservation　of　anammox　granular　sludge　(AnGS)　is　an　essential　approach　to　support　the　sustainable　development　of　anammox　processes.　In　this　study,　the　activity　descent　and　its　mechanism　of　AnGS　during　long-term　cryopreservation　were　investigated.　The　results　showed　that　the　cryopreservation　process　of　AnGS　could　be　divided　into　plummeting　stage,　maintaining　stage　and　descending　stage　in　terms　of　activity　index,　namely　three-stage　activity　descent.　A　significant　positive　correlation　was　observed　between　the　ATP　pool　and　the　three-stage　activity　descent　(by　hzo-mRNA/hzo-gene　ratio)　of　AnGS　(R2　=　0.944).　The　ATP　pool　was　found　to　be　replenished　by　the　sequential　consumption　of　endogenous　energy　substances,　leading　to　the　stationary　activity　of　AnGS.　The　consumption　of　essential　cell　components　as　an　energy　source　was　revealed　to　cause　damage　and　even　death　of　functional　bacteria,　and　the　energy　stress　could　be　mitigated　by　the　regular　exogenous　substrate　supply.　Consequently,　the　energy　support　in　terms　of　ATP　could　be　a　feasible　way　to　innovate　the　preservation　tech-nology　and　promote　the　sustainable　development　of　anammox　processes.