For reliability optimization during the development of X-ray flat panel detectors, this study proposes a multi-dimensional reliability enhancement testing method. Two flat panel detectors were selected as test subjects. Considering their actual service environments, eight stress-loading tests were designed and conducted, including low-temperature stepping, high-temperature stepping, rapid temperature variation, vibration stepping, constant humidity heat stepping, constant humidity heat limit, alternating humidity heat, and comprehensive environmental tests. A dark-field grayscale measurement system was established to monitor performance variations. The results show that both detectors maintained stable operation across the full temperature range. In the vibration stepping test, detector-1 exhibited a temporary disconnection at 10 grms but was recoverable, whereas detector-2 experienced irreversible failure at 8 grms. Under 95%RH conditions, both detectors functioned normally. However, detector-1 failed and could not recover under the comprehensive environmental test, indicating that multi-factor coupled environments significantly accelerate damage. Microscopy and X-ray transmission characterization revealed that solder joint cracking, PCB fractures, wire misalignment, and surface contamination were the primary failure modes, and that the synergistic effects of mechanical stress and humidity markedly accelerated material aging and interfacial degradation. Based on these findings, we propose improvements in soldering-process optimization, cleanliness control, printed-circuit-board anti-vibration design, and chip-wire fixation, thereby providing insights and references for enhancing the reliability of X-ray flat panel detector design and manufacturing.