At present, there are some conception confusions about organization, team and group, and also team formation is still in qualitative analysis phase in multi-robot field. The paper, using Markov course and evolution calculation theory for reference, researches the difference between team and organization in conception and the formation mechanism of robot team from cooperative entity layer and ability layer. This paper proposes and describes a dynamic evolution model about robot team formation. There hasn't been a similar model at home and abroad now. The model can not only wholly describe robot team, but also quantitatively describe dynamical evolution course of the team formation.