Right to detain any vessel is granted to the coastal states by UN Convention in the Law of the Sea (1982). On the contrary, the right to put forward an application for the prompt release is granted to the flag states. This matter can also be found in the General Principals of Law. Therefore not only the members of the convention are committed to abide by but also each country is obliged to do so. In this line some cases were raised to International Tribunal of the Law of the Sea (ITLOS) and decisions were made. The present paper is an attempt to study the different aspects of such prompt release and its securities based on the 1982 convention, ITLOSs decisions and General principals of law. The obtained result can be applied to the next cases of ITLOS and countries future relations.At last, the terms of prompt release and reasonable bond are brought to light in short based on Iranian internal law in relation to the International law.