Preventing a chemical vapor deposition (CVD) chamber from particle contamination in which a higher low-frequency radio frequency (LFRF) power and longer process time are provided to vacate the chamber and perform a pre-heat process. Following that, a pre-oxide layer is formed on the chamber wall, while a high-frequency radio frequency bias is provided to the chamber. The high-power LFRF is continuously provided to the chamber to sustain the temperature of the chamber, and then a main oxide layer deposition process is performed. The method is able to form an oxide layer of better quality on a CVD chamber wall, so as to solve the particle problem in the prior art. Therefore, yield is improved and the maintenance cost is reduced.