Cyber Physical Systems solve complex problems through their tight integration between the physical and computational components. Therefore, the reliability of a complex system is the most critical requirement for the cyber physical system because an unreliable system often leads to service disruption, property dam-age, financial loses and sometimes lead to fatality. In order to develop more reliable CPS, this paper proposes a generic framework for reliability modeling and analysis for our ongoing work on cyber physical systems.This paper, at first defines an architecture for general CPS which is comprised of three layers; environment layer, communication layer, and computational layer. Secondly, we formalize a reliability model for the architectural components, and then propose a framework for the reliability of CPS with the consideration of how to capture the reliability. Based on the research method, we demonstrate the proposed frame-work with an illustrative example by using different reliability values from offshore and onshore reliability data library. We confirmed that the reliability model covers almost all possible reliabilities required to general cyber-physical systems.