In order to study the natural vibration characteristics of floating offshore win d turbine systems, the finite element method is used. Taking a 3 MW floating off shore wind turbine for example, the distribution of mode shapes and the parameter analysis of t he natural frequencies and are investigated. The calculation equatio ns used to estimate the fundamental frequency and the overturning frequency are fitt ed based on a series of parametric analyses. The results show that the fundament al frequency is directly proportional to the anchorage depth of the inhaul cable and the blade length, and inversely proportional to the buoy radius. The fun damental frequency also has a quadratic relationship with the total crosssecti onal area of the inhaul cable and the tower height. The relationship between the overturning frequency and parameters involves highorder term, so it is more complica ted. The good agreement between the results from the fitting equation and the resu lts from the finite element method indicates that the fitting equation has a high credibility in predicting the natural frequencies of floating offshore wind turbines.