Over the last few decades, reliability engineering has been successfully applied in many industries to improve the performance of equipment maintenance management. Many optimization models and researches are developed and widely used to achieve a high level of maintenance, i.e. the balance of performance, risk, resources, and cost to achieve an optimal solution. although, the application of these techniques to medical equipment is very new,One of the major challenges is how to improve the safety, security and reliability of medical devices. In this paper a FMEA based assessment model is proposed to improve human reliability in medical devices. Fuzzy linguistic variables are used to express the experts’ evaluation for risk factors of sub systems. The results indicate that the human reliability assessment of medical devices must be more focused on reducing soft failures and hidden risks. Also through the designing and developing processes of medical devices, attention must be paid to the communication between operators and designers.