In this paper the reliability issue of a solar array of LEO spacecraft was analyzed with Failure Modes Effects and Criticality Analysis (FMECA) to ensure that the solar array will deliver the required power to the spacecraft until the end of life without failures. The main failure modes, their effects and criticalities were illustrated. A fault tree was built. Both qualitative and the quantitative analysis of the fault tree were performed. The probability of the top event, the structural importance and the critical importance coefficients of different basic events were detected and overcome by protective actions. According to the analyses, the main reasons of the satellite solar array failure and the list of the critical components were presented. The effects of different failures were classified according to the severity and the criticality of the faults. Recommendations for improving solar arrays' reliability were provided for reliability design and structure improvement of the satellite solar array.