In the LUND model, the explanations of e+e-- --> qqgBAR --> 3jets and
Y --> 3g --> h's are based on the application of the LUND string fragm
entation model to the color string structures of qqgBAR and 3g systems
. In this paper, starting from the color wave functions of the qqgBAR
and 3g systems, these color string structure are directly studied by u
sing QCD. It is shown that the reasonableness and accuracy of the LUND
string picture are revealed.