Abstract: Crack propagation velocity is a crucial discussion for understanding dynamic fracture. Classical dynamic fracture theory predicts a “forbidden velocity zone” for mode Ⅱ cracks, i.e., the velocity between the Rayleigh and shear wave speeds. However, supershear transition has been demonstrated theoretically and experimentally for mode-Ⅱ crack constrained to weak interfaces. Such transition is commonly accepted to be governed by the Burridge-Andrews mechanism (also known as “mother-daughter” crack), which predicts direct nucleation of a secondary intersonic daughter crack induced at the Rayleigh wave speed. Nevertheless, to our knowledge, “mother-daughter” crack pairs are rarely reported with visual observations, and the supershear rupture without the daughter crack forming has also been found in some previous reports. Recently, Prof. Liangbin Li’s group at University of Science and Technology of China and the coworkers reported the Sub-Rayleigh to supershear transition of dynamic mode-Ⅱ cracks based on numerical simulations. Their numerical experiments successfully reproduced the “mother-daughter” cracks for the first time in phase-field fracture modeling, as well as the supershear transition without the daughter crack. Given that, a crack tip blunting-tearing hypothesis was presented to explain that cracks comply with different mechanisms from Sub-Rayleigh to supershear regimes, and a critical prestress level was revealed below which no supershear transition can be accomplished from the Sub-Rayleigh propagation. Furthermore, the criteria were also proposed for predicting the occurrence of the daughter crack through systematic simulations. This paper briefly presents their progress in the studying of the Sub-Rayleigh to supershear transition for dynamic mode-Ⅱ interfacial fracture.