On the Definition and Adopted Parameters of International Terrestrial Reference Frame 2000

Definition, main parameters, conditions and realization for the international terrestrial reference system 2000 (ITRS2000) and international terrestrial reference frame (ITRF2000) are studied. The differences and characteristics between ITRF2000 and the previous ITRFyy in the history are pointed out and emphasized. Besides, the relationships, including their transformation parameters among the previous ITRFyy are also given in the paper.