Based on the quantum molecular dynamics model, we investigate the dynamical
behaviors of the excited nuclear system to simulate the latter stage of he
avy ion reactions, which associate with a liquid-gas phase transition. We t
ry to search a microscopic way to describe the phase transition in real nuc
lei. The Lyapunov exponent is employed and examined for our purpose. We fin
d out that the Lyapunov exponent is one of good microscopic quantities to d
escribe the phase transition in hot nuclei. Coulomb potential and the finit
e size effect may give a strong influence on the critical temperature. Howe
ver, the collision term plays a minor role in the process of the liquid-gas
phase transition in finite systems.