  Recent type Ia supernovae data seem to favor a dark energy model whose
equation of state $w(z)$ crosses -1, which is a much more amazing problem than
the acceleration of the universe. Either the case that $w(z)$ evolves from
above -1 to below -1 or the case that $w(z)$ runs from below -1 to above -1, is
consistent with present data. In this paper we show that it is possible to
realize the crossing behaviours of both of the two cases by only a single
scalar field in frame of Dvali-Gabadadze-Porrati braneworld. At the same time
we prove that there does not exist scaling solution in a universe with dust.
