  The debate on conservation laws in general relativity eighty years ago is
reviewed and restudied. The physical meaning of the identities in the
conservation laws for matter plus gravitational field is reexamined and new
interpretations for gravitational wave are given. The conclusions of these
studies are distinct from the prevalent views, it can be demonstrated that
gravitational wave does not transmit energy (and momentum) but only transmits
informations. An experimental test is offered to decide which conservation laws
are correct.
