  By means of the quark mass density- and temperature- dependent model, it is
found that the negative charge and the higher strangeness fraction are in favor
of the stability of strange quark matter at finite temperature. A critical
baryon number density n_Bc has been found. The strange quark matter is unstable
when n_B < n_Bc. The charge and strangeness fraction dependence of stability
for strange quark matter is addressed.
