The macroscopic and microscopic fracture characteristics and energy evolution laws of weakly cemented sandstone are explored. Multi-dimensional testing technologies were utilized. These technologies included XRD component testing, nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), rock mechanics tests, and CT scanning. A multi-scale characterization method was constructed. The quasi-phase transformation evolution characteristics and macro-micro fracture mechanisms of weakly cemented sandstone were systematically studied. Significant quasi-phase transformation behavior is observed in weakly cemented sandstone during the loading process. The initiation and termination of this evolution are correlated with the volumetric strain dilatancy point and the maximum dilatancy angle point, respectively. An expanding trend is exhibited by the strain ratio interval between these two critical states with an increase in confining pressure. During the quasi-phase transformation process, rock mass damage is dominated by crack propagation and deformation. The stress level at the rock strain sudden-increase point is determined to be in the range of 90% pre-peak to 90% post-peak. This determination is based on the maximum crack propagation energy. With the improvement of the cementation degree, the deformation and failure characteristics of the rock mass are shifted from large deformation to small deformation. The energy release is transitioned from low energy to high energy. The damage evolution mechanism is transformed from cementation structure weakening by tension to cementation material destruction by compression and shear.Based on the above characteristics, corresponding roadway support concepts are proposed for different working conditions. For strata with high in-situ stress (≥20MPa) and a high cementation degree, a "yielding while resisting" support mode is adopted. The post-peak plastic softening zone is selected as the support control interval. For strata with low in-situ stress (≤10MPa) and a low cementation degree, a support mode of "first improving surrounding rock, then controlling before resisting" is adopted. The weakly cemented surrounding rock is required to be controlled by the support before the completion of the quasi-phase transformation. For other working conditions, a "first controlling, then yielding, and finally resisting" support mode is adopted. The surrounding rock control is required to be completed before the strain sudden-increase point of the surrounding rock. In addition, the quasi-phase transformation interval in weakly cemented surrounding rock strata is broadened by strong active support. Large deformation and high energy release events after the quasi-phase transformation are suppressed. Meanwhile, the construction cost of passive support is reduced. The collaborative optimization of support effects and engineering economy is realized.