The crystallization of nanosized amorphous silicon nitride powder is one of the methods to produce sub-micrometer/nanosized alpha-Si3N4 powder. The application of this method is still limited by the long crystallization time, low output, and high cost. This article invents a new crystallization method of amorphous silicon nitride involving the addition of Si powder. The new process reduces the complete crystallization time from more than 6 h to 30 min, thus allowing efficient production of sub-micrometer/nanosized alpha-Si3N4 powder. Effects of factors such as additive, temperature, and duration on the crystallization process are investigated using XRD and FTIR. The experimental results showed that the added Si powder accelerates the crystallization process effectively. The final product is a mixture of alpha-Si3N4 and Si2N2O. In this article, amorphous silicon nitride powder with added Si is annealed at 1450 degrees C. Powder of nearly 100% crystalline phase content is produced either by adding 10% Si and annealing for 15 min or by adding 5% Si and annealing for 30 min.