We detected the Free Core Nutation (FCN) directly and revealed the time variation of FCN from the analysis of the Very Long Baseline Interferometry (VLBI) observation for the period 1979.9-2000.1. We developed the model of the FCN which consider both the energy dissipation due to the viscosity of fluid core and the magnetic coupling of core-mantle boundary and the excitations during the observation period. From the analysis of VLBI data, we discovered that the FCN is of the damped oscillation which had 4 significant excitations at 1989.90 ± 0.40, 1994.47±0.40, 1994.76±0.40, and 1998.99±0.40. And then these epochs roughly coincide with the occurrence of some huge earthquakes, namely whose amplitude are bigger than Mw 8.0.