  The mixed quark-gluon condensate is another chiral order parameter in QCD,
which plays an important role in the application of QCD sum rules. In this
letter, we study the properties of quark-gluon mixed condensate at finite
temperature and quark chemical potential in the framework of global color
symmetry model. Using an infrared-dominant model gluon two-point function, we
find that the behavior of quark-gluon mixed condensate at finite temperature
and chemical potential is similar to that of the quark condensate, and both of
them give the same information about chiral phase transition. We also find that
the ratio of these two condensates is insensitive to the temperature and
chemical potential, which supports the conclusion obtained recently by the
authors using quenched lattice QCD (They only studied the nature of the mixed
quark-gluon condensate at finite temperature).
