The silicon nitride films have been deposited by Electron Cyclotron Resonance-plasma enhanced chemical vapor deposition (ECR-PECVD) method at low temperature, and the pure nitrogen is introduced into the ECR chamber as the plasma gas, the silane(Ar diluted, Ar:SiH4=19:1) is used as precursor gas. The optimum deposition parameters of SiN films for photovoltaic application as an efficient antireflection coating(ARC) have been investigated. The actual composition of the films will be varied with the deposition conditions, such as gas flow rate ratio(N2/SiH4), substrate temperature, and microwave power. The effect of deposition parameters on the optical performance of SiN films was determined by Ellipsometry. The Si-N and N-H stretching characteristic peaks of SiN films have been observed by FTIR spectroscopy. Results shown that uniform silicon nitride films with low hydrogen content can be deposited at high deposition rate(10.7nm/min), and the refractive index increased with the increasing of substrate temperature and microwave power. The film shows good optical properties (refractive index is 2.0 or so) and satisfied surface quality (average roughness is 1.45nm) when the deposition parameter is 350oC and microwave power is 650W.