Objective To explore the clinical characteristics of acute kidney injury (AKI) by different causes and to evaluate the patients' outcomes. Methods We searched for the renal function indicators of all the inpatients of Changzheng Hospital in 2011 by the hospital information management system, screened AKI patients according to KDIGO criteria, reviewed the medical histories of AKI patients and divided them into pre-renal, intrinsic-renal and post-renal AKI according to different causes, and then we analyzed the clinical features of the AKI patients and evaluated their outcomes. Results A total of 278 AKI patients were involved in this study and the overall incidence of AKI was 0.896%. The cases with pre-renal, intrinsic-renal and post-renal AKI were 200(71.9%), 63(22.7%) and 15(5.4%), respectively. Significant differences were found among the three groups concerning age, basic serum creatinine (sCr) and peak sCr (P<0.05). The detection rates had a significant difference among three groups (P<0.05), with that of intrinsic-renal AKI patients being the highest (28.6%, 18/63). Among the three groups, the renal replacement therapy rate was the highest in the intrinsic-renal group (17.5%, 11/63). The pre-renal AKI occurred most frequently in liver transplantation department, the intrinsic-renal AKI was frequently found in nephrology department, and the post-renal AKI was in neurosurgery department. Logistic regression analysis showed that the AKI stage was a risk factor for death and renal function prognosis in the pre-renal AKI patients, and age and AKI stage were the risk factors for renal function recovery in the patients with the intrinsic-renal AKI. Conclusion The incidence of pre-renal AKI is the highest, and it occurs frequently in liver transplantation department. AKI stage is the risk factor for the prognosis of the patients with pre-renal AKI. The basic sCr and peak sCr are higher in the intrinsic-renal AKI than in pre- and post-renal AKI. The intrinsic-renal AKI occurs frequently in nephrology department and it can be easily caused by drugs. Age and AKI stage are the risk factors for renal function recovery in the pre-renal AKI patients. The outcome of post-renal patients is the best.