In a liquefied natural gas (LNG) terminal operation, the reduction of boil-off gas (BOG) is critical for economy and safety. The BOG recondenser, which is a key piece of equipment for dealing with BOG, is commonly used in receiving terminals. The dynamic behavior of a BOG recondenser is complex and difficult to stabilize. Therefore, an exact dynamic model of the equipment needs to be developed that will help improve the operation. In this research, we propose an advanced dynamic modeling methodology for BOG recondensers using HYSYS dynamics to achieve better accuracy than previous studies. The main feature of the proposed methodology is that variable flash efficiency depending on the LNG input rate is allowed, enabling the description of non-equilibrium phenomena inside the recondenser. The proposed methodology was verified by using the operating data from the BOG recondenser in a real terminal, and it showed less than 2% errors in the measurements of the liquid level, temperature, and pressure.