  Bilayer (BL) molybdenum disulfide (MoS$_2$) is one of the most important
electronic structures not only in valleytronics but also in realizing
twistronic systems on the basis of the topological mosaics in Moir\'e
superlattices. In this work, BL MoS$_2$ on sapphire substrate with
2$H$-stacking structure is fabricated. We apply the terahertz (THz) time-domain
spectroscopy (TDS) for examining the basic optoelectronic properties of this
kind of BL MoS$_2$. The optical conductivity of BL MoS$_2$ is obtained in
temperature regime from 80 to 280 K. Through fitting the experimental data with
the theoretical formula, the key sample parameters of BL MoS$_2$ can be
determined, such as the electron density, the electronic relaxation time and
the electronic localization factor. The temperature dependence of these
parameters is examined and analyzed. We find that, similar to monolayer (ML)
MoS$_2$, BL MoS$_2$ with 2$H$-stacking can respond strongly to THz radiation
field and show semiconductor-like optoelectronic features. The theoretical
calculations using density functional theory (DFT) can help us to further
understand why the THz optoelectronic properties of BL MoS$_2$ differ from
those observed for ML MoS$_2$. The results obtained from this study indicate
that the THz TDS can be applied suitably to study the optoelectronic properties
of BL MoS$_2$ based twistronic systems for novel applications as optical and
optoelectronic materials and devices.
