Abstract: Objective To explore the clinical hazards of acute kidney injury（AKI）in Inner Mongolia. Methods The authors retrospectively reviewed the electronic medical records of Inner Mongolia Autonomous Region People’s Hospital and Hohhot First Hospital. AKI was confirmed by the changes in blood creatinine levels according to the guideline of Kidney Disease：Improving Global Outcomes. Results The subjects were divided into five age subgroups of<75 years，≥75，<80 years，≥ 80，<85 years，≥85，<90 years and ≥90 years. Mortality rates were 1. 3%、2. 4%、3. 3%、4. 9%、 5. 9%；Length of hospital stay for non-AKI and AKI patients was 15（11，23）and 17（10，31）days； Length of hospital stay for community-acquired AKI（CA-AKI）and hospital-acquired AKI（HA-AKI） 11（5，19） and 21（12，36） days；Inpatient medical expenses of non-AKI and AKI patients 19505 （11241，41404）yuan and 44，312（19 324，93 553）yuan；Hospitalization expenses for CA-AKI and HAAKI 51，949（23 873，106 235）and 27，400（12 982，60 964）yuan；AKI was independently associated with in-hospital mortality in all age subgroups. OR values were 5. 540（95% confidence interval 4. 459-6. 883），4. 099（95% confidence interval 2. 785-6. 032），4. 986（95% confidence interval 3. 556-6. 992）， 5. 885（95% confidence interval 3. 985-8. 692）and 4. 894（95% confidence interval 2. 603-9. 202）. Conclusion Regarding the relationship between AKI and length of stay，total hospital expenses and inhospital all-cause mortality，hospitalization expenses are higher in AKI patients. Patients with HA-AKI have longer hospital stays and AKI patients carry a higher risk of in-hospital mortality. And AKI is independently associated with in-hospital mortality by age stratification.