Abstract: The completely conservative difference scheme for hyperbolic differential equations in three dimensions is studied. The parameter algorithm is introduced for three dimensional Eulerian hydrodynamic equations. It is shown that the parameters have to satisfy some conditions if the completely conservative difference schemes are to be constructed. It is proved that these schemes have second order accuracy. And the schemes with undetermined parameters are constructed for the three dimensional Eulerian equations of non viscous, non conducting, compressible fluid flow.