  Hawking radiation of the blackhole is calculated based on the principle of
local field theory. In our approach, the radiation is a unitary process,
therefore no information loss will be recorded. In fact, observers in different
regions of the space communicate using the Hawking radiation, when the systems
in the different regions are entangled with each other. The entanglement
entropy of the blackhole is also calculated in the local field theory. We found
that the entanglement entropy of the systems separated by the blackhole horizon
is closely connected to the Hawking radiation in our approach. Our calculation
shows that the entanglement entropy of the systems separated by the horizon of
a blackhole is just a pure number $\frac{\pi^3 + 270 \zeta(3)}{360 \pi^2}$,
independent of any parameter of the blackhole, and its relation to the Hawking
radiation is given by $S_{EE} = \frac{8 \pi}{3} \frac{\pi^3 + 270
\zeta(3)}{\pi^3 + 240 \zeta(3)} {\cal A} R_H$, where $S_{EE}$ is the
entanglement entropy, $\cal A$ is the area of the horizon, and $R_H$ is the
Hawking radiation.
