  Our goal is to understand the nature of blazars and the mechanisms for the
generation of high-energy $\gamma$-rays, through the investigation of the
blazar 3C 66A. We model the high energy spectrum of 3C 66A, which has been
observed recently with the Fermi-LAT and VERITAS telescope. The spectrum has a
hard change from the energy range of 0.2-100 GeV to 200-500 GeV in recent
almost contemporaneous observations of two telescopes. The de-absorbed VERITAS
spectrum greatly depends on the redshift, which is highly uncertain. If z=0.444
is adopted, we are able to use the SSC model to produce the Fermi-LAT component
and the EC model to the VERITAS component. However, if z=0.1, the intrinsic
VERITAS spectrum will be softer, there will be a smooth link between the
Fermi-LAT and VERITAS spectra which can be explained using a SSC model.
