[en] Understanding the interface effect on the thermal transport properties in black phosphorus (BP)/SiO₂ heterojunctions is of funcamental importance for developing BP-based nanoelectronic devices. Here, we present a bond relaxation method to illustrate an atomic-level insight into the size-dependent interface thermal transport properties of BP/SiO₂ heterojunctions. It has been found that the decrease of BP membrane thickness could enhance interface adhesion energy as well as interface coupling strength in BP/SiO₂ heterojunctions, which leads to an enhanced interface thermal conductance. The theoretical predictions provide a possible method on interface thermal transport properties of BP-based heterostructures for potential applications. (paper)