Abstract: Ejected particles, especially slags, from solid rocket motors (SRMs) are an important issue in the risk assessment and the structural protection design of spacecraft. This paper reviews the development of SRM slag models: NASA Approach, MIT/LL Laboratory Approach, and MASTER2005 Slag Model. The number and the mass of slags obtained by the MASTER model are both lower than those of the NASA model, and according to the MASTER model, about 91.8% of the slags have a diameter in the range of 25～200 mm, but those with diameter larger than 250 mm account for 88% of the total mass and only 6.3% of the total number. According to these models, the number and mass distributions of slag debris can be analyzed to serve as a technical basis for further research on the space debris environment.