Collaborative Virtual Environment (CVE) is a promising technology which provides people a 3D shared virtual world over the networks, where participants can interact with each other more naturally. However, the scalability of existing CVE system is limited due to the constraints in processing power and network speed of each participating host. On the other hand, mobile agent is a new paradigm for the network-centric programming which can implement distributed applications in an open and dynamically changing environment. In this paper, a mobile agent-based architecture for Large-scale CVE (LCVE) is proposed to support a large number of concurrent participants in a VE with a large amount of evolving virtual entities. The LCVE software system is made up of mobile agents. And each mobile agent will be responsible for an independent task for the LCVE. With the mobility and autonomy of mobile agents, LCVE software system will be extensible; the workload in the LCVE will be balanced dynamically; the management of LCVE contents will be autonomous at agent level.