  Swift J1644+57 is an unusual transient event, likely powered by the tidal
disruption of a star by a massive black hole. There are multiple short
timescales X-ray flares were seen over a span of several days. We propose that
these flares could be produced by internal shocks. In the internal shock model,
the forward and reverse shocks are produced by collisions between relativistic
shells ejected from central engine. The synchrotron emission from the forward
and reverse shocks could dominate at two quite different energy bands under
some conditions, the relativistic reverse shock dominates the X-ray emission
and the Newtonian forward shock dominates the infrared and optical emission. We
show that the spectral energy distribution of Swift J1644+57 could be explained
by internal shock model.
