  TianQin is a space-based gravitational-wave observatory scheduled to be
launched in the 2030s. In this work, we make a preliminary forecast for the
cosmological parameter estimation with the gravitational-wave standard siren
observation from TianQin. We simulate the standard siren data of TianQin based
on its 5-year observation after the completion of construction. In the
simulation, three models for the population of massive black hole binary
(MBHB), i.e., pop III, Q3nod, and Q3d, are considered to predict the event
numbers of MBHB mergers. We find that: (i) among the three MBHB models, the
Q3nod model can provide the tightest constraints on the cosmological
parameters; (ii) TianQin's standard siren observation can effectively break the
parameter degeneracies inherent in the cosmic microwave background observation;
and (iii) the future standard siren observation from TianQin can significantly
improve the cosmological parameter estimation under the current mainstream
electromagnetic observations.
