Nowadays, with the changing landscape of the population, the family structure and the advancement of medical care technology, the average life expectancy keeps lengthening. The elder population ratio in Taiwan is forecasted to grow in a fast path to 14.4% in 2019. This growing trend of more aged population indicates the needs of elder care as well as the demands of high quality medical devices. Medical device has direct impact on human safety and therefore, the risk analysis and mitigation on the design and production of medical devices are highly regulated by the governments around the world. Two international standards: ISO 13485 and ISO 14971 indicate respectively the requirement of risk analysis for medical device manufacturer and how the risk analysis is implemented. Failure Mode Effect Analysis (FMEA) is one of the risk analysis tools to analyze the dangers and risks. However, traditional FMEA assumes independence among risk factors which can lead to negligence and misjudgment by the analyzer. This study applies a modified FMEA method that considers dependent factors. The relative effects of the risk factors among factors (effects) or itself (feedback) can then be analyzed, allowing the analyzer to perform risk control procedures, to decide what activities to perform or prioritize more effectively to increase the quality and reliability of the medical device. In the study, the modified FMEA is implemented in the design phase of a medical device, the results shows clear dependence of risk factors. The proposed threshold value is used to differentiate the risk factors if their RPN numbers are equal, and it gives a more realistic evaluation of risk factors.