With the wind power development gradually going to the deep water area， the floating offshore wind turbine （FOWT）shows great advantages. However， the SPAR-type FOWT， which is more mature around the world， is usually in deeper draft.Due to the limitation of water depth in the China offshore areas， this technology can hardly be directly adopted. To overcome this issue， a new-type reduced-draft SPAR-type foundation is proposed for 100-meter-depth offshore area. Based on the three dimensional potential theory， the hydrodynamic performance is analyzed. Furthermore， its dynamic performance under different scenarios of mooring fracture is studied. The motions of the wind turbine and the mooring tension are simulated in the time domain， after one mooring line of the FOWT is broken. Moreover， the influence of mooring pretension and the wind turbine operational status on the motion of FOWT is investigated. According to the results， the FOWT could work normally in the offshore areas where the water depth is 100 m， but the large drift motion is observed after the mooring line of the FOWT is fractured. This will severely influence other wind turbine in the same wind farm， and it has potential threats on the nearby ships.