Aging kidney undergo structural changes such as increasing percentages of glomerular sclerosis, vascular sclerosis. Functional changes such as reduced ultrafiltration coefficient with increased glomerular capillary pressure and decreased glomerular filtration rate (GFR) and chronic comorbidities increases susceptibilities to acute kidney injury (AKI). The incidence of AKI has continuously increased over the past decades, owing to the increased recognition of AKI diagnosis, increased aged population, co-morbidities, and increased exposure of polypharmacy. However, mortality rates have decreased reflecting improvements of patients care such as dialysis. The survivor of AKI is also increasing, and this population continue to suffer long term effects associated with AKI: recurrence of AKI, progression to chronic kidney disease (CKD), increasing risk of cardiovascular disease, hospital admissions, and long-term mortality. Previous studies have reported that rapid recovery of AKI is associated with better short-term survival. Coca et al. showed that rate of mortality for the patients with AKIN stage 1 with a duration longer than 7 days was more than 2- fold higher than patients with AKIN stage 3 with <2 days. Prognosis is related to duration of AKI as well as AKI severity. Non-recovery of AKI at hospitalization is highly associated with increasing mortality risk. Late recovery of AKI was related to better outcomes than non-recovery, and worse than early recovery of AKI. And old age is always a potent risk factor of late recovery, non-recovery of AKI and progression to CKD. Most commonly used measure for assessing renal recovery is serum creatinine. Serum creatinine dose not accurately predict of renal recovery for older population because of loss of muscle mass, malnutrition, and hyperfiltration with increasing glomerular sclerosis. Older patients may impair renal cell regeneration and reestablishment of polarity. Older patients were related to persistent inflammation and renin-aldosterone system activation with underlying cardiovascular disease, these lead to AKI to CKD transition. The 28~34 % of AKI survivors experienced a second AKI episode. And recurrent AKI is related to increased 1- year mortality. AKI may cause cardiac dysfunction and cardiovascular events, and related to long term mortality. We need to follow up the patients after the recovery of AKI, and further research is crucial to stratify high risk patients especially in older population.