  In this paper, we study the evaporation dynamics of the Sachdev-Ye-Kitaev
(SYK) model, with an initial temperature $T_\chi$, by coupling it to a thermal
bath with lower temperature $T_\psi<T_\chi$ modeled by a larger SYK model. The
coupling between the small system and the bath is turned on at time $t=0$. Then
the system begins to envolve and finally becomes thermalized. Using the Keldysh
approach, we analyze the relaxation process of the system for different
temperatures and couplings. For marginal or irrelevant coupling, after a
short-time energy absorption, we find a smooth thermalization of the small
system where the energy relaxes before the system become thermalized. The
relaxation rate of effective temperature is found to be bounded by $T$, while
the energy thermalization rate increases without saturation when increasing the
coupling strength. On the contrary, for the relevant coupling case, both energy
and effective temperature show oscillations. We find this oscillations
frequency to be coincident with the excitation energy of a Majorana operator.
