  In this letter, we clarify the algebra expression for calculating the quark
condensate based on the non-perturbative quark propagator calculated through
Schwinger-Dyson equation. The quark condensates, which characterize the low
energy QCD vacuum, should not get a divergent quantity at large energy scale;
the re-normalization group evolution behaviour at large energy scale therefore
should be interpreted as "smeared collective effects" for it contains both
perturbative and non-perturbative parts.
  We prefer the integral expression and get a quantity which is both convergent
and scale dependent.
