This paper analyzes the effect of behavior convention in agent group. An emergence approach to the convention formation through the propagation and evaluation of plans is presented, which is based on the effect analysis for the convention to the utility of single agent. This approach is able to generate complex conventions and suited to open environments. It is also jibe with the autonomy of agent. A quantitative model for the propagation of conventions is given out, with which the disseminating rate of convention is studied.