Acute kidney injury (AKI) is a commonly encountered syndrome associated with high mortality and poor outcomes. With high rate of missed diagnosis and inadequate treatment, AKI has not received as much attention in clinical practice. The key to improve the prognosis of AKI is early diagnosis and intervention. Firstly, there should be careful consideration to identify those people at greatest risk for AKI and treat the modifiable risk factors. Secondly, several biomarkers of AKI, which can reflect the early changes of the kidney function, such as kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, urinary N-acetyl-β-D-glucosaminidase, and so on, have been applied to clinical practice. Other methods of accessory examination, including urine microscopy, Doppler-based renal arterial resistive index, and quick measurement of GFR based on portable fluorescence analyzer, were also reported to play important roles in the early diagnosis of AKI. Lastly, combined with electronic health records and clinical information system, the electronic alert system for AKI has aroused great concern among clinicians and been applied to the practical management of AKI gradually. This article reviewed the above issues for assisting AKI early diagnosis.