Existing approaches on reliability assessment of the sys- tem entirely depends on expertise, knowledge of system an- alysts and computation of usage probability of different user operations. Existing approach is therefore can not be taken as accurate, particularly to deal with new or unfamiliar sys- tems. Further modern systems are very large and complex to manipulate without any automation. Addressing these is- sues, we propose an analytical technique in our work. In this paper, we propose a novel approach to assess reliabil- ity of the system using use case model. We consider a metric to assess the reliability of a system under development. Keywords: Reliability assessment, reliability metric, use case model.