  The Tianlai experiment is dedicated to the observation of large scale
structures (LSS) by the 21 cm intensity mapping technique. In this paper we
make forecasts on its capability at observing or constraining the dark energy
parameters and the primordial non-Gaussianity. From the LSS data one can use
the baryon acoustic oscillation (BAO) and the growth rate derived from the
redshift space distortion (RSD) to measure the dark energy density and equation
of state. The primordial non-Gaussianity can be constrained either by looking
for scale-dependent bias in the power spectrum, or by using the bispectrum.
Here we consider three cases: the Tianlai cylinder array pathfinder which is
currently being built, an upgrade of the pathfinder array with more receiver
units, and the full-scale Tianlai cylinder array. Using the full-scale Tianlai
experiment, we expect $\sigma_{w_0} \sim 0.082$ and $\sigma_{w_a} \sim 0.21$
from the BAO and RSD measurements, $\sigma_{\rm f_{NL}}^{\rm local} \sim 14$
from the power spectrum measurements with scale-dependent bias, and
$\sigma_{\rm f_{NL}}^{\rm local} \sim 22$ and $\sigma_{\rm f_{NL}}^{\rm equil}
\sim 157$ from the bispectrum measurements.
