  The velocity and density distribution of $e^\pm$ in the pulsar wind are
crucial distinction among magnetosphere models, and contains key parameters
determining the high energy emission of pulsar binaries. In this work, a direct
method is proposed, which might probe the properties of the wind from one
pulsar in a double-pulsar binary. When the radio signals from the first-formed
pulsar travel through the relativistic $e^\pm$ flow in the pulsar wind from the
younger companion, the components of different radio frequencies will be
dispersed. It will introduce an additional frequency-dependent time-of-arrival
delay of pulses, which is function of the orbital phase. In this paper, we
formulate the above-mentioned dispersive delay with the properties of the
pulsar wind. As examples, we apply the formula to the double pulsar system PSR
J0737-3039A/B and the pulsar-neutron star binary PSR B1913+16. For PSR
J0737-3039A/B, the time delay in 300\,MHz is $\lesssim10\mu$s near the
superior-conjunction, under the optimal pulsar wind parameters, which is $\sim$
half of the current timing accuracy. For PSR B1913+16, with the assumption that
the neutron star companion has a typical spin down luminosity of
$10^{33}$\,ergs/s, the time delay is as large as $10\sim20\mu$s in 300\,MHz.
The best timing precision of this pulsar is $\sim5\mu$s in 1400\,MHz.
Therefore, it is possible that we can find this signal in archival data.
Otherwise, we can set an upper-limit on the spin down luminosity. Similar
analysis can be apply to other eleven known pulsar-neutron star binaries
