To study the effects of particle size and content of Al powders on the particle damping generated by nitrate ester plasticized polyether (NEPE) propellant combustion products, the condensed phase combustion products of NEPE propellant were collected by a sealed bomb method and the particle size analysis was performed. The particle damping of combustion products on acoustic instability was calculated according to the theory of Culick linear particle damping. Results show that the particle size and content of Al powders significantly affect the particle damping of NEPE propellant combustion products on acoustic instability combustion, which mainly is due to the particle size and content of Al powders affect the particle size distribution of condensed phase combustion products. For a certain frequency acoustic instability combustion, the higher the mass fraction of particle in [1/2D_opt, 2D_opt] particle size interval in the condensed phase combustion products is, the greater the efficiency coefficient of particle damping of combustion products is, the larger the produced particle damping is. The mass fraction of condensed phase combustion products in combustion products is one of the factors determining the scale of particle damping, and which is positively correlated with the content of Al powders in propellant.