 Acute kidney injury is more frequent than before and the incidence rate was about 35-50 in hospital. The mortality rate would be as high as 50-60 when the renal replacement therapy was needed. Many studies about the timing of start and discontinuation of dialysis, dialysis dose, dialyzer, anticoagulation and dialysates were initiated but the results were still controversial. In addition, more new biomarkers were found to predict the outcome of acute kidney injury and these biomarkers may play an important role for the dilemma of aforementioned studies 