  We report an experimental study of quench dynamics across the superfluid
transition temperature $T_c$ in a strongly interacting Fermi gas by ramping
down the trapping potential. The nonzero quasi-condensate number $N_0$ at
temperature significantly above $T_c$ in the unitary and the BEC regimes
reveals the pseudogap physics. Below $T_c$, a rapid growth of $N_0$ is
accompanied by spontaneous generation of tens of vortices. We observe a power
law scaling of the vortex density versus the quasi-condensate formation time,
consistent with the Kibble-Zurek theory. Our work provides an example of
studying emerged many-body physics by quench dynamics and paves the way for
studying the quantum turbulence in a strongly interacting Fermi gas.
