Taiji, a space-based gravitational-wave observatory, consists of three satellites forming an equilateral triangle with arm length of $3\times {10}^6$ km, orbiting around the Sun. Taiji is able to observe the gravitational-wave standard siren events of massive black hole binary (MBHB) merger, which is helpful in probing the expansion of the universe. In this paper, we preliminarily forecast the capability of Taiji for improving cosmological parameter estimation with the gravitational-wave standard siren data. We simulate five-year standard siren data based on three fiducial cosmological models and three MBHB growth and formation models. It is found that the standard siren data from Taiji can effectively break the cosmological parameter degeneracies generated by the cosmic microwave background (CMB) anisotropies data, especially for dynamical dark energy models. The constraints on cosmological parameters are significantly improved by the data combination CMB+Taiji, compared to the CMB data alone. Compared to the current optical cosmological observations, Taiji can still provide help in improving the cosmological parameter estimation to some extent. In addition, we consider an ideal scenario to investigate the potential of Taiji on constraining cosmological parameters. We conclude that the standard sirens of MBHB from Taiji will become a powerful cosmological probe in the future.

太极天基重力波天文台由三颗卫星组成，等边三角形的臂长为 $3\times {10}^6$公里，绕太阳公转。太极能够观察到大规模黑洞二进制（MBHB）合并的重力波标准警报事件，这有助于探测宇宙的膨胀。在本文中，我们初步预测了引力波标准警报数据对太极拳改善宇宙学参数估计的能力。我们基于三个基准宇宙学模型和三个MBHB生长和形成模型来模拟五年标准警报器数据。研究发现，太极的标准警报数据可以有效地打破宇宙微波背景（CMB）各向异性数据产生的宇宙学参数简并性，特别是对于动态暗能量模型而言。与仅CMB数据相比，CMB + Taiji数据组合大大改善了对宇宙学参数的约束。与目前的光学宇宙学观测相比，太极仍可以在一定程度上改善宇宙学参数估计。此外，我们考虑了一个理想的场景来研究太极拳在约束宇宙学参数方面的潜力。我们得出的结论是，太极MBHB的标准警报器将在将来成为强大的宇宙探测工具。