High-concentration alumina particle jet can erode the surface of the solid propellant inside a solid rocket motor under some special conditions such as flight acceleration. Because of lack of effective testing methods, knowledge of the combustion characteristics of solid propellants under dense-particle erosion conditions is very limited. In this study, the combustion characteristics of hydroxyl-terminated polybutadiene and nitrate ester plasticized polyether propellants were investigated using real-time X-ray radiography technology and an overload simulation erosion motor. The high-temperature dense-particle jet can cause erosive burning of the solid propellants. No clear threshold velocity is found for the particle erosive burning, and the erosive burning rate increases with the particle velocity. The erosion of the dense-particle jet includes the heat flux increment effect and mechanical damage effect, and the particle erosive burning is mainly caused by the heat flux increment effect of the particles. Numerical simulation results show that the particles can impact the propellant surface at a very low speed and cause heat flux increments; this explains the lack of a clear threshold velocity for the particle erosive burning of solid propellants. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.