The nature of Brillouin-enhanced four-wave mixing (BEFWM) temporal modulating behavior is examined numerically. The evolution of the acoustic wave, which plays a key role in the process of energy inter-coupling, is simulated and analyzed. Based on this, the detailed mechanism of BEFWM temporal characteristics is explained. It is demonstrated that, modulations in the conjugate wave are related with the distribution and fluctuation of the acoustic wave, and influenced by parameters such as phonon lifetime, intensity of the signal and pump wave, effective interaction length, and so on.