Investigations on the oxygen contamination in the μc_Si∶H thin films deposited by very_high_frequency plasma_enhanced chemical_vapor deposition(VHF_PECVD) technique with and without load lock chamber have been reported in this paper. From the results of x_ray photoelectron spectroscopy and Fourier transform infrared absorption measurements, it can be identified that oxygen exists in μc_Si∶H film with different bonding modes, namely Si—O bonding, O—H bonding and O—O b onding. In addition, the influences of oxygen on the structural and electrical p roperties of the films are studied with Raman spectra, conductivity(σ) and acti vation energy (Ea) measurements. The results reveal that structural propertie s of the μc_Si∶H film depend strongly on the bonding modes of the existing oxy gen. The electrical properties show that the role of oxygen in μc_Si∶H films i s different from those in a_Si∶H and the essential mechanism needs to be furthe r explored.