  How to distinguish the zero-bias peak (ZBP) caused by the Majorana fermions
from that by the other effects remains a challenge in detecting the topological
order of a quantum wire. In this paper we propose to distinguish the
topological superconducting phase from the topologically trivial phase by
making a Josephson junction of the quantum wire attached to a side lead and
then measuring the tunneling conductance through it as the phase difference
across the junction $\phi$ varies. Even if the ZBPs exist in both phases, we
can identify the topological superconducting phase by a conductance peak at
$\phi=\pi$ and a nearby butterfly pattern.
