  H.E.S.S. observed TeV blazar PKS 2155--304 in a strong flare state in 2006
July. The TeV flux varied on timescale as short as a few minutes, which sets
strong constraints on the properties of the emission region. By use of the
synchrotron self-Compton model, we found that models with the bulk Lorentz
factor $\sim 100$, the size of the emission region $\sim 10^{15}$ cm, and
magnetic field $\sim 0.1$ G explain the observed spectral energy distribution
and the flare timescale $\sim$ a few minutes. This model with a large value of
$\Gamma$ accounts for the emission spectrum not only in the TeV band but also
in the X-ray band. The major cooling process of electrons/positrons in the jet
is inverse Compton scattering off synchrotron photons. The energy content of
the jet is highly dominated by particle kinetic energy over magnetic energy.
