Non-stoichiometric silicon nitride (SiNx) thin films are deposited on p-type crystalline silicon substrates at low temperature (200 ℃) using ammonia and silane mixtures by plasma enhanced chemical vapor deposition. The evolutions of SiN, SiH and NH bonding configurations, the variations of Si 2p and N 1s electron binding energy and the ratio R of nitrogen to silicon atoms in SiNx films annealed at temperature in a range of 5001100 ℃ are investigated at room temperature by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. The relationship between the evolutions of FTIR and XPS spectroscopy of the samples at different annealing temperatures and the variations of bonding configurations of Si, N and H atoms is discussed in detail. According to the arguments about FTIR and XPS spectroscopy we conclude that when the annealing temperature is lower than 800 ℃, the breakings of SiH and NH bonds in the SiNx films lead mainly to the formation of SiN bonds; when the annealing temperature is higher than 800 ℃, the breakings of SiH and NH bonds are conducible to the effusion of N atoms and the formation of silicon nanoparticles; when the annealing temperature equals 1100 ℃, the N2 react on the SiNx films to cause the ratio R of nitrogen to silicon atoms to inerease. These results are useful for controlling the probable chemical reaction in SiNx films under high annealing temperatures and optimizing the fabrication parameters of silicon nanoparticles embedded in SiNx films.