  We present an explanation for the unusual temporal feature of the GRB 030226
afterglow. The R-band afterglow of this burst faded as ~ t^{-1.2} in ~ 0.2 days
after the burst, rebrightened during the period of ~ 0.2 - 0.5 days, and then
declined with ~ t^{-2.0}. To fit such a light curve, we consider an
ultrarelativistic jetted blast wave expanding in a density-jump medium. The
interaction of the blast wave with a large density jump produces relativistic
reverse and forward shocks. In this model, the observed rebrightening is due to
emissions from these newly forming shocks, and the late-time afterglow is
caused by sideways expansion of the jet. Our fitting implies that the
progenitor star of GRB 030226 could have produced a stellar wind with a large
density jump prior to the GRB onset.
