Abstract: Parylene is a conformal coating material bearing excellent performance,widely used in aviation,aerospace,electronicfield. This paper describes the research procedure and result about insulating property of different parylene coating. Three kinds ofcoating as parylene C, parylene N, and parylene D with different thickness were prepared by vacuum vapor deposition technique,whose insulating performance is compared later. Besides, insulating performance change of the three kinds of coating under normalcondition, temperature shock, and damp-heat test is studied. A technical support for the application of parylene coating in electronic component protection is provided in this paper.