Amorphous silicon nitride films were deposited by low-frequency plasma-enhanced chemical vapor deposition(LF-PECVD) using silane and nitrogen as precursors. Characteristics such as deposition rate, surface morphology, and chemical composition were measured by spectroscopic ellipsometry(SE), atomic force microscope(AFM) and x-ray photoelectron spectroscopy(XPS). It was shown that amorphous silicon nitride film could be prepared by LF-PECVD with good uniformity and even surface. The XPS result indicated that a small quantity of oxygen was involved in the sample, which was discussed in this paper.