Abstract: Object oriented design and development are well-known conceptions in today’s software development environment. Object oriented design supports number of design properties such as coupling, cohesion, inheritance and encapsulation. The proposed study will deliver a method for reliability measurement of object oriented design in term of complexity perspective. The four metrics namely Inherited Complexity Metric, Cohesion Complexity Metric , Encapsulation Complexity Metric ,Coupling Metric, are identified for each of object oriented design properties such as inheritance, cohesion coupling, and encapsulation respectively. Complexity and reliability measurement approach is presented in this research paper. On the basis of identified metrics a multiple linear regression equation has been established for measuring the complexity of design structure. Complexity is directly affects reliability of object oriented designs in opposite direction. Finally a multiple regression equation has been applied to measure reliability with respect to complexity. Comparative analysis between metric values, reliability and complexity has been done in this study.Complexity, Reliability, Design Phase, Measurement.