Abstract: There exists no homogeneous system of international law because it consists of erratic blocks and elements, differentpartial systems, and universal, regional，or even bilateral subsystems and subsub systems of different levels of legal inte-gration. The system of international law has become increasingly fragmented, particularly since it has developed in recentdecades ．Such an “unorganized system” is full of intra-systematic tensions, contradictions and frictions. The MOX Plantcase demonstrates the conflicts between international tribunals which are resulted from proliferation of international courtsand tribunals. The harmonization of jurisdictions of different international tribunals is tough and critical for integratingfragmentation of international law.

Key words: Fragmentation of International Law, Proliferation of International Courts and Tribunals, Exclusive Ju-risdiction, Compulsory Jurisdiction, optional Jurisdiction