System Architecture evaluation and formal specification are the significant processes and practical endeavors in all domains. Many methods and formal descriptive techniques have been proposed to make a comprehensive analysis and formal representation of a system architecture. This paper consists of two main parts, in first we evaluated system performance, quality attribute in Remote Temperature Sensor clients-Server architecture by implementing an ATAM model, which provides a comprehensive support for evaluation of architecture designs by considering design quality attributes and how they can be represented in the architecture. In the second part, we computed the selected system architecture in ISO standards formal description technique LOTOS with which a system can be specified by the temporal relation between interactions and behavior of the system. Our proposed approach improves on factors such as ambiguity, inconsistency and incompleteness in current system architecture.