This paper uses the theory proposed by Professor Bin Cheng with respect to subject of international law as the tool to explain how Taiwan can participate in Regional Fishery Management Organizations (RFMOs), in the capacity of fishing entity. As long as States wish, a non-State entity can become subject of international law and participate in international organizations in the ways agreed upon by States through constituent instrument of the organization. Fishing Entity is a term created by the 1995 United Nations Fish Stocks Agreement for Taiwan to participate in RFMOs. Taiwan has been using this term to participate in different RFMOs with different status, e.g., Member of the Commission, Member of the Extended Commission, and Cooperating non-Contracting Party, Entity, or Fishing Entity. The difference of the wills of States as demonstrated in different RFMOs' constituent instruments provide such different status that Taiwan has in different fora.