Using SiH4 and H2 as sources, we use hot-wire chemical vapor deposition to prepare intrinsic amorphous silicon (a-Si∶H) on c-Si wafers surface. Quasi-steady state photo conduction method and I-V method are used to analyze the influence of process parameters on the passivation effect. C-V method and deep level transient spectroscopy (DLTS) method are employed to test the defect state of the passivated silicon wafer surface. The experimental results show that, under the condition of 200 kHz, the surface defect density of the c-Si wafer with surface recombination velocity of 54 cm/s is 1.02×1011 eV-1·cm-2 and the fixed charge density is 6.12×1011 cm-2. The passivation effect of a-Si∶H on the surface of the silicon wafer is determined by the dangling bond on the surface of the thin film silicon saturated by hydrogen bond and the surface fixed charges forming the field passivation effect. The a-Si∶H passivated deep-level defect on the surface of the wafer is characterized as electron trap. The active energy, capture cross section and defect concentration is 0.235 eV, 1.8×10-18 cm2, and 4.07×1013 cm-3, respectively.