Summary: A reliability evaluation method based on belief reliability is developed. Belief reliability is a reliability metric which incorporates the influence of design margin, aleatory uncertainty and epistemic uncertainty, therefore, it can be used to measure products, reliability in presence of epistemic uncertainty. First, the evaluation method for epistemic uncertainty factors based on performances of product’s failure mode and effects analysis is proposed. Next, a belief reliability evaluation procedure which considers design margin, aleatory uncertainty and epistemic uncertainty is developed. Finally, a case study of a power circuit is conducted to demonstrate the developed methods. The results show that the confidence in product’s reliability is reduced by the influence of epistemic uncertainty.