As naval vessel speed up, a new propulsion system is needed to overcome the problems of propeller propulsion system. Therefore, the water jet propulsion system, which can solve these problems, was adopted as a new propulsion system for a high-speed naval vessel. In the case of naval vessel with water jet propulsion system, the test method is not unified, such as requiring a self propulsion test according to ITTC 1987, 1996, or ITTC's latest report, including resistance test. In addition, the water jet performance estimation method published after ITTC 1996 directly measures the performance parameters of the water jet, and has problems in cost as well as difficulty in measuring and interpreting the results. Therefore, the accuracy of the ITTC 1987 method should be evaluated and reflected when designing a naval vessel. In this paper, when designing a naval vessel with a water jet propulsion system, the water jet performance estimation method proposed by ITTC 1987 is applied and the required power is estimated to compare whether the design method is appropriate or not with an real naval vessel.