Abstract: Inner ear hair cells are the receptor cells for sound and balance sensation in animals, responsible for transducing mechanical signals into electrical signals, a process referred to as mechanoelectrical transduction (MET). Hair cell is named after the hair bundle on its apical surface, which consists of one tubulin-based kinocilium and dozens of actin-based stereocilia. Kinocilium plays an important role in the development of hair bundle, while stereocilia are indispensable for MET. In each hair cell, the stereocilia are organized into several rows of increasing heights, forming a staircase-like pattern. The development and maintenance of stereocilia is tightly regulated. In recent years, the rapid progress in proteomics, transcriptomics, and super-resolution microscopy has shed light on the underlying mechanism of stereocilia height regulation, but a lot more awaits further investigation. In the present review, we focus on what is known about the mechanism of stereocilia height regulation.