The efficient development of coalbed methane (CBM) resources is of great significance for advancing the energy transition. However, the embedment behavior and quantitative characterization of multi-sized proppants remain key challenges in CBM fracturing design. This study investigates the embedment process of proppants under five placement patterns based on the placement behavior of three commonly used proppant size classes in vertical fractures. Proppant embedment depth was measured using strain gauges and digital image correlation (DIC), while acoustic emission (AE) monitoring was used to investigate damage evolution and energy release during embedment. Three AE-based indicators, namely the unloading count ratio (), the early reactivation coefficient (), and the stepwise increment coefficient (), were introduced to identify the evolution stages of proppant embedment. An elastoplastic embedment model for multi-sized proppants was further established based on Hertzian contact theory and Tabor’s concept and then validated against experimental data. The results show that proppant embedment gradually evolves from elastic-dominated to plastic-dominated deformation with increasing stress, and that multi-sized proppants exhibit smaller embedment depths than single-sized proppants under the same stress level. AE activity shows a progressive temporal evolution; when 13% or < 0.85, accompanied by 2.0, the system exhibits signs of local instability, typically corresponding to concentrated proppant embedment. The proposed model agrees well with the experimental data, with a root mean square error of 0.027. The model shows that embedment depth is closely related to proppant placement pattern. This study provides a theoretical basis for CBM development design.