  In high-energy nuclear collisions, the production of light nuclei is
sensitive to the temperature and phase-space density of the system at
freeze-out. In addition, the phase transition from QGP to the hadronic phase
will lead to large baryon density fluctuation, which will be reflected in the
light nuclei production. For example, the ratio of proton ($N(p)$) and triton
($N(t)$) to deuteron ($N(d)$) yields, which is defined as
$N(t)$$\cdot$$N(p)$/$N^2(d)$, may be used as a sensitive observable to search
for the QCD critical point. In this paper, we will report the energy dependence
of light nuclei ($d$, $t$) production in Au+Au collisions at $\sqrt{s_{NN}}$
=7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV measured by the STAR
experiment at RHIC. We will present the beam energy dependence for the
coalescence parameter $B_2(d)$ and $B_3(t)$, particle ratios ($d/p$, $t/p$, and
$t/d$), and the yield ratio of $N(t)$$\cdot$$N(p)$/$N^2(d)$. Their physics
implications will be discussed.
