[en] A Friction Pendulum System (FPS) is a well known seismic isolation system. In the case of FPS, the period of a vibration only depends on a radius of a curvature and the gravitational constant, and it does not depend on the mass. For this reason, the FPS is useful for smaller weight equipment and a liquid storage tank which changes its' liquid level. Kim et al. (2004) studied the seismic isolation effect of small equipment by using a natural rubber bearing (NRB), a high damping rubber bearing (HDRB) and a Friction pendulum system (FPS) by an experimental research. In this study, modified Mokha model for a small FPS system was proposed and it was revealed this model matched the experimental results well