Most of the charging piles run in harsh environments such as outdoor for a long time, and are prone to reliability problems, which has become one of the bottlenecks affecting the development of new energy automobile industry. Taking the classic DC charging pile as an example, the reliability index of the DC charging pile is proposed. In-depth analysis of the reliability impact of the internal structural function modules of the DC charging pile, and the minimum cut set method was used to calculate the failure index of the DC charging pile. The calculation example calculates the reliability indicators such as the failure rate of the charging pile through specific parameters to verify the effectiveness of the method in this paper.