  We study in this Letter the origin of the confinement in QCD by analyzing the
colour charge of physics states. We derive the colour charge operator in QCD
and compare it with the electromagnetic charge operator in QED. It shows that
the two charges have very similar structure, but the dynamical properties of
the gauge fields are different. The difference between the behaviours of the
gauge boson propagator at zero momentum for QCD and that for QED guarantees
that there occurs colour confinement in QCD but there is no confinement in QED.
We give then a universal relation between the confinement and the dynamical
property of QCD and reveals the origin of the colour confinement, which can be
demonstrated as the dynamical effect of QCD or more explicitly the dynamical
mass generation of the gluon.
