Due to its merits including high energy density, high operating voltage and low memory effect, lithium-ion (Li-ion) battery has been widely applied in different systems. As the power units, to ensure reliable operation of the systems, it is crucial to gain an efficient method for the evaluation of battery performance. Health indicators (HIs), which refer to the indexes extracted from the monitoring signals, can characterize the ageing of an item and help to solve such issues. Taking the Li-ion battery as the research object, this paper systematically reviews the definition and classification of HIs on the basis of existing literatures. Taking the capacity and internal resistance of Li-ion battery as the criteria, the HIs are divided into direct HIs and indirect HIs as a whole. On this basis, the direct and indirect HIs are further grouped with more details. In addition, some major HIs are evaluated from the view of the battery aging and the difficulty of extraction. After that, the advantages and disadvantages of HIs are analyzed. Finally, some future direction for the development of HIs is proposed.