This research is conducted through monitoring 27 5-years-old children and interviewing 3 preschool teachers to find out when confronting peer group trouble, preschool teachers would resort “Intervention After trouble” under which condition; if so, what’s kind of “Intervention After trouble” and the influence of the intervention behavior on the formation of peer group after the trouble. The result shows that when preschool teachers realize after they intervened once but the relationship between the parties did not return to what it was before, they would adopt “Intervention After trouble”. The “Intervention After trouble” can be divided as early stage direct intervention and latter indirect intervention. The intervention behavior act as a bridge for communication needed for formation of peer relationship. The result implies “Intervention After trouble” is an indispensable part if preschool teachers want to establish peer group respecting the children’s spontaneity.