Based on macro-time and micro-time, a BDI-Agent model with branch time tree is defined. In this model, parallel actions in macro-time are interleaving in micro-time. The mental state of Agent is constructed on macro-time, and the semantics of concurrent actions are given in micro-time level. Thus, it can be a proper logic basis for describing multi-Agent cooperation and competition that involve concurrent, and it can advance the work in Agent models developed by Rao & Georgeff, Singh and Werner et al.