  Temperature dependence of relaxation dynamics of UX$_{3}$ (X = Al, Ga, Sn)
compounds is studied using time resolved pump-probe technique in the
reflectance geometry. UGa$_{3}$ is an itinerant antiferromagnet, while
UAl$_{3}$ and USn$_{3}$ are spin fluctuation systems. For UGa$_{3}$, our data
are consistent with the formation of a spin density wave SDW gap as evidenced
from the quasidivergence of the relaxation time $\tau$ near the N\'{e}el
temperature $T_{N}$. For UAl$_{3}$ and USn$_{3}$, the relaxation dynamics shows
a change from single exponential to two exponential behavior below a particular
temperature, suggestive of coherence formation of the 5\textit{f} electrons
with the conduction band electrons. This particular temperature can be
attributed to the spin fluctuation temperature $T_{sf}$, a measure of the
strength of Kondo coherence. Our $T_{sf}$ is consistent with other data such as
resistivity and susceptibility measurements. The temperature dependence of the
relaxation amplitude and time of UAl$_{3}$ and USn$_{3}$ were also fitted by
the Rothwarf-Taylor model. Our results show ultrafast optical spectroscopy is
sensitive to c-\textit{f} Kondo hybridization in the \textit{f}-electron
systems.
