  A two-components isospin lattice gas model has been employed to study the
liquid-gas phase transition for asymmetric nuclear matter. An additional degree
of freedom, namely, the asymmetry parameter alpha has been considered carefully
for studying the phase transition. We have shown that under the mean field
approximation, the liquid-gas phase transition given by this model is of second
order. The entropy continues at the phase transition point. The binodal surface
is addressed.
