Reliability is the key characteristics of any efficient software system. Most of the software system fails due to noreliable in nature. Evaluating reliability is one of the main functions of the software system. Since last decades, the popularity of object oriented software system is increased in exponential ways. Many methods or models have been developed for reliability evaluation but few of them took considerations of object oriented features. In this paper, fuzzy approach is used to evaluate reliability. Due to reliable in nature, CK metrics are used in reliability measurement. Based on the case studies performed on object oriented software, it is concluded that we can choose reliable software very easily among various available software system.