Statistical properties of slamming pressure acting on a Very Large Floating Structure (VLFS) has been investigated experimentally in this research. The bottom pressure, the displacement and the acceleration at the tip of the elastic model were measured in irregular waves. The elastic model is 1/150 scale of a VLFS which is planned in the Mega-Float project in Japan. The spectrum analysis and the statistical analysis of the measured data have been carried out. Results shows that the responses in irregular waves are almost linear and slamming can be treated as a separable phenomena. the statistical analysis shows that the bottom pressure in the sea of return period 200 years is small enough compared with the value of a conventional ship. On the contrary, the acceleration at the tip is not negligible.