  The broadband afterglow of GW170817/GRB 170817A is believed to be from an
off-axis structured jet. The central engine of a gamma-ray burst usually
launches a pair of outflows that move oppositely, it is reasonable to consider
the emission from a double-sided structured jets, with a near-jet moving toward
us and a counter-jet moving away from us. Assuming that the two branches of the
jet have the same physical parameters, we have calculated their radio emission.
It is found that the counter-jet component will emerge in the radio light
curves $\sim$ 2500 days post-merger.It typically leads to a plateau in the
light curve, thus could be hopefully revealed by high accuracy radio
observations. We have also considered the possibilities that both branches have
different parameters, and found that if some of the physical parameters of the
counter-jet are evaluated more favorably than those of the near-jet, then the
counter-jet emission will be enhanced and will clearly show up as an obvious
plateau or even a rebrightening. For example, when the circum-burst medium
encountered by the counter-jet is assumed to be 100 times denser than that of
the near-jet, a remarkable radio plateau will appear at $\sim$ 600 days.
However, in X-ray bands, the counter-jet component is generally too faint to be
discerned. It is argued that the late radio observations of GW170817/GRB
170817A can help determine the key parameters and diagnose the environment of
the event.
