  The pointwise space-time behavior of the Green's function of the
three-dimensional relativistic Boltzmann equation is studied in this paper. It
is shown that the Green's function has a decomposition of the macroscopic
diffusive waves and Huygens waves with the speed $\sqrt{a^2+b^2}$ at
low-frequency, the singular kinetic wave and the remainder term decaying
exponentially in space and time. In addition, we establish the pointwise
space-time estimate of the global solution to the nonlinear relativistic
Boltzmann equation with non-smooth initial data based on the Green's function.
