The investigation of overlapping impacts and resultant erosion is of great significance for improving the AAJ micromachining performance of brittle and difficult-to-machine materials. In this work, a computational model coupling the Monte Carlo (MC) method and discrete element method (DEM) is developed to study the erosion process of micro-hole fabrication on glass using abrasive air jet (AAJ) at a 90° impact angle. We employ the MC method combined with probability distribution functions to model the impinging particle flow. Brittle erosive behaviors of the overlapping impacts between the impacting particles and the target specimen are simulated by the DEM model. The modeling framework is firstly validated by experimental results using patterns and sizes of micro-holes on the specimen. We then conduct mechanism investigations on the particle and crack behaviors in the erosion process and the overlapping condition effect in the multiple impacts. The relationship between the jet characteristics with the machining efficiency and surface quality of micro-holes is further discussed. The results indicate that the presented DEM model can capture the particle interference effects, which play an essential role in controlling the material removal and microstructure geometry in AAJ machining. The model and findings can help understand the microscopic erosion mechanism and optimize the processing performances of microstructures on brittle materials in AAJ.