Quantum information technology requires bright and stable single-photon emitters (SPEs). As a promising single-photon source, SPEs in layered hexagonal boron nitride (hBN) have attracted much attention recently for their high brightness and excellent optical stability at room temperature. In this review, the physical mechanisms and the recent progress of the quantum emission of hBN are reviewed, and the various techniques to fabricate high-quality SPEs in hBN are summarized. The latest development and applications based on SPEs in hBN in emerging areas are discussed. This review focuses on the modulation of SPEs in hBN and discusses possible research directions for future device applications.