The n-type sulfur-doped diamond film has been synthesized on substrate of p-type silicon wafer (p-Si) by glow plasma assisted chemical vapor deposition (CVD). In situ diagnosis of plasma environment for synthesizing diamond film was conducted by Langmuir single probe and optical emission spectroscopy. The surface morphology, microstructure, and components of the films were characterized by the scanning electron microscopy (SEM), x-ray diffraction (XRD), Raman and the atomic force microscopy (AFM). The semiconductor type and electric properties of films were analyzed based on the Hall Effect measurement. Some important results are as follows: (1) The high-quality nanocrystalline diamond film without doping was obtained at low deposition temperature. The experimental conditions for system of [CH_4+H_2] have been optimized. (2) Based on the results obtained from the measurements of Langmuir single probe and optical emission spectroscopy, the mechanism of diamond growth was theoretically investigated via Monte Carlo method. (3) The n-type sulfur-doped diamond film was prepared on (111) p-Si substrate, and the I-V curve measured across the interface between the n-type diamond and p-Si substrate demonstrates the p-n junction behavior.