Abstract: The processes of the interaction between the liquid phase and solid phase when specially designed samples of low carbon steel was being brazed under selected technological parameters by three different kinds of NiCrBSi system were directly and continuously observed and recorded by the authors with HM-100 type high temperature microscope.Three kinds of different dynamic process of interaction had been discovered. The mechanism of the interaction and the conditions of changeover from one kind to another among the three processes were advanced.