By integrating a single-time relativistic quantum transport equation o
ver momentum, we derive the hydrodynamic equation of motion from a qua
ntum field theory including full spin structure of Dirac particles. Th
e results are the continuity equation, energy equation and the general
ized force law of a relativistic plasma. The equation of velocity fiel
d and spin density show however more complex structures than those der
ived from quantum mechanics.