The leaching behavior of R7T7 borosilicate glasses with different waste loading amounts was evaluated via hanging the static immersion method at different temperatures and two leaching systems (i.e., deionized water and simulated North Mountain groundwater) for 365 days. The changes of etched layer phases, morphology, and composition with leaching time were also analyzed by X-ray diffractometry, scanning electron microscopy-X-ray energy spectrometry, and inductively coupled plasma mass spectrometry. The results show that the glass starts to appear in heterogeneous phases when the loading amount of waste exceeds 20%, and its composition is mainly molybdenum-rich materials and noble metals. The results of leaching experiments reveal a positive correlation between the mass loss rate of the glass and the leaching temperature. In the initial leaching phase, the three elements Na, Si, and B were leached at a higher rate in deionized water rather than in simulated Beishan groundwater, while after equilibration the three elements were leached at comparable rates in both leaching agents. The surface of the glass has a variety of crystalline phases generated after 365 days of leaching, mainly in spherical, floral, and prismatic and honeycomb morphologies, consisting mainly of components such as Mg-Si-O and Si-Nd-Gd-O. Based on the analysis above, the leaching process of glass solid is controlled due to the ion diffusion mechanism and glass network dissolution mechanism. The results of these studies can provide the data to support the future safety evaluation of high-level radioactive glass waste in geological disposal processes.