Abstract: Root hairs are tubular extensions of plant root epidermal cells that play vital roles in soil fixation, water and inorganic salts absorption, and information exchange between plant roots and outside world. The developmental processes of root hair are highly plastic and might easily be affected by various plant hormones and environmental factors. Due to the structural and functional characteristics of root hair, it is often used as model to study apical growth and fate determination of plant cells. Therefore, the regulatory mechanism of root hair development has been a hot topic in the field of botany. The review summarized the research progress in the field of root hair development in the past two decades.