Silicon nitride (SiNx) thin films were deposited by DC pulse reactive magnetron sputtering at ambient temperature. These films were characterized by spectroscopic ellipsometry(SE), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). It is found that among several regulable parameters, pulse frequency, target power density, reactive gas flow rate (or working pressure) could significantly influence the optical properties and compositions of SiNx thin film more than the reverse time. The rotation of substrate which used to improve the uniformity in the radial direction also can be utilized to alter the in-depth composition distribution of the films. SiNx film with high refractive index (~2.00) and ultra low extinction coefficient (<10-3) were obtained on the optimal deposition conditions. It could be concluded that, compared to many disadvantages existing in various chemical vapour deposition (CVD) or radio frequency (RF) magnetron sputtering, DC pulse reactive magnetron sputtering is an alternative method to produce SiNxfilms for the increasing application especially as the moisture barriers for flexible electronics and optoelectronics.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.