  We explore the prospects of detecting of Galactic double white dwarf (DWD)
binaries with the space-based gravitational wave (GW) observatory TianQin. In
this work, we analyze both a sample of currently known DWDs and a realistic
synthetic population of DWDs to assess the number of guaranteed detections and
the full capacity of the mission. We find that TianQin can detect 12 out of
$\sim100$ known DWDs; GW signals of these binaries can be modeled in detail
ahead of the mission launch, and therefore they can be used as verification
sources. Besides we estimate that TianQin has potential to detect as many as
$10^4$ DWDs in the Milky Way. TianQin is expected to measure their orbital
periods and amplitudes with accuracies of $\sim10^{-7}$ and $\sim0.2$,
respectively, and to localize on the sky a large fraction (39%) of the detected
population to better than 1 deg$^2$. We conclude that TianQin has the potential
to significantly advance our knowledge on Galactic DWDs by increasing the
sample up to 2 orders of magnitude, and will allow their multi-messenger
studies in combination with electromagnetic telescopes. We also test the
possibilities of different configurations of TianQin: (1) the same mission with
a different orientation, (2) two perpendicular constellations combined into a
network, and (3) the combination of the network with the ESA-led Laser
Interferometer Space Antenna. We find that the network of detectors boosts the
accuracy on the measurement of source parameters by 1-2 orders of magnitude,
with the improvement on sky localization being the most significant.
