Design of offshore wind turbine foundation involves multi-disciplinary fields and contains various subitems, so software is often needed to assist designing. On the other hand, marine engineering design software and finite element analysis software is not specifically developed for offshore wind turbine foundation, then make it very necessary to develop professional software. The design process and main contents of foundation design is firstly introduced, the software's main functions including load calculation, combination of load, pile analysis, foundation analysis and result output have to be developed to achieve the above requirements. The kernel modules contain visualization function, integrated designing, foundation input and reconfigurable computing. Then calculation methods and main principle embedded in software is introduced. Lastly application of software FDOW to design offshore wind turbine foundation is given with one practical project.