Abstract: In order to describe the aluminum agglomeration process more clearly and quantitatively, a chain reaction model is proposed by analogy with the chain reaction in polymer chemistry. In this model, the agglomeration process can be divided into three steps: initiation step (breaking of oxide membrane on aluminum powder surface), propagation step (bollision of aluminum powders and agglomeration) and termination step (ignition). The formulae of aluminum agglomeration rate, mean degree of agglomeration and distribution of agglomerating powder diameters are provided. They can predict the effects of burning rate, combustion chamber pressure, AP particle size, aluminum powder size and percentage on the agglomeration degree. The trends of all predictions by the provided formulae are consistent with the experimental researches.