Nowadays, utilization of high efficiency and low emission of pollution power production systems is one of the primacies and attractive topics for researchers. Solid oxide fuel cells are such systems; the capability of them to integrate with power cycles such as gas turbine cycles proposes a hybrid system for future power plant. This study examined the performance of a natural-gas-fed tubular solid-oxide fuel cell combined with a conventional recuperative gas turbine power plant. Then the overall system performance was analyzed by analyzing the different components separately; and further applying thermodynamic laws for the entire cycle. The results of performance of the power plant for certain operating conditions were compared against those available in the literature. The comparisons provided useful verification of the thermodynamic simulations in the present work. Then, in contrary with the previous studies, the base SOFC/GT hybrid system was combined with water injection method. Next, second law based performance analysis including irreversibility determination of the hybrid system was performed. Also, a parametric study was performed to illustrate the effects of various parameters such as compressor Pressure ratio, fuel mass flow rate, entropy generation rate, SOFC power, electrical power and CO 2 emission. By means of this system, it is possible to reach a first law efficiency around 62% and the second law efficiency about 60%. The overall power, the first law efficiency and the second law efficiency of this system were increased up to 6.5%, 4.5% and 5.6%, respectively. Key Words Solid oxide fuel cell, Gas turbine, hybrid, Water injection, performance, exergy, CO 2 emission.