Lanthanide-based single-molecule magnets (Ln-SMMs) have distinctive potential applications in spintronic devices, ultra-high-density information storage and quantum information processing due to the peculiar structure and large intrinsic magnetic anisotropy. Despite the recent remarkable breakthroughs in extending the magnetic blocking temperatures (TB) of Ln-SMMs, significant challenges still exist in achieving higher magnetization reversal barriers (Ueff) and practical application. With the primary objective of promoting development of SMMs, dysprosium-based SMMs (Dy-SMMs) have emerged as extraordinary candidates for constructing high performance SMMs thanks to their large magnetic moment and anisotropy. Meanwhile, quantum tunneling of magnetization (QTM) can be eliminated by introducing magnetic interaction, thereby improving Ueff. Among Dy-SMMs, dinuclear dysprosium SMMs (Dy2-SMMs) have been selected as the simplest model to investigate the effect of magnetic interaction on QTM. However, the former researches indicated that the relaxation mechanisms of Dy2-SMMs and the factors of slow magnetic behavior remain unclear. Hence, this review attempts to elucidate the intricate relaxation mechanism, and the strategies for synthesizing and manipulating Dy2-SMMs are discussed in details. Ultimately, the development of multifunctional materials based on Dy2-SMMs are discussed in this review. This work aims to explore the relaxation mechanisms and magneto-structural correlations of Dy2-SMMs and present inspiration for enlightening their properties as well as designing new multifunctional magnets.