With the continuous development of wireless communication technology, the application of array antennas is becoming increasingly widespread. For high-precision electronic products like array antennas, their reliability is a critical consideration in the product lifecycle. Improving the reliability of array antennas requires an initial assessment of their operational reliability, identifying vulnerable aspects, and subsequently researching targeted solutions. This paper begins by summarizing and analyzing the characteristics of fault mode data for array antennas. Building upon previous research on reliability assessment methods, a new quantitative reliability evaluation method specifically tailored for array antennas is proposed. The application of this method is demonstrated through a concrete example, contributing to a comprehensive evaluation of the reliability of array antennas. This study provides valuable insights and guidance for enhancing the reliability of array antenna products.