Floating offshore wind turbine (FOWT) have great potential in the field of offshore wind energy development. However, the capital cost of offshore wind power is still an important challenge that restricts its scale and commercialization process. In order to improve the mooring efficiency and economic benefits of FOWT, in this paper, the OC3 Hywind mooring system of NREL 5MW offshore floating generator set is taken as the research objective. A novel design method of multiline shared anchor is studied, that is, FOWTs in wind farms share anchors instead of being moored separately. The multiline anchor load (net force) is computed as the vector sum of the contributing mooring line tensions, and time domain simulations is performed in SIMA RIFLEX, analyze the dynamic response and evaluate the cost of the multiline shared anchor mooring system, the results of research show that: (1) For large scale offshore wind farms, using 3-line and 4-line shared anchor design can reduce the number of anchors required by 66.7% and 75%, respectively. (2) In terms of dynamic response, compared with the conventional single-line mooring, the 3-line and 4-line anchor load of shared anchor design is reduced, respectively. (3) The specific cost of shared anchor system was calculated, and the results show that for large-scale wind farm with 100 FOWTs, the mooring anchor cost could be reduced by 53.96% and 68.65% by adopting the design of 3-line and 4-line shared anchor, so as to provide reference for the application of shared mooring in offshore wind farm.