Ocean thermal energy conversion system uses from water in surface of the ocean as high temperature source and water in the depth of the ocean as low temperature source. Three types of ocean thermal energy conversion systems including close cycle, open cycle and hybrid systems are available. In a close cycle system, working fluid through a thermodynamic cycle based on the Rankine cycle can rotate the turbine and generate electricity. Due to the variation in the ocean surface temperature, the output power of the ocean thermal energy conversion system is not fixed and controllable and so this uncertainty nature results in the numerous states in the generated power of this plant. Thus, in integrating ocean thermal energy conversion systems to the power system, many aspects of power system such as reliability may be affected and so new approaches must be developed for investigation these effects. In this regard, in this paper for the first time, the reliability of power system containing ocean thermal energy conversion system is evaluated and the valuable indices such as loss of load expectation, expected energy not supplied and peak load carrying capability that can be used for generation expansion planning of power system, are calculated.