With the increasing requirements for Distributed Virtual Environment (DVE): supporting larger number of participants and providing more smooth roaming and interactions, scalability is becoming a key issue. In this paper, we explore the scalability of participants and the scalability of servers, and mainly focus on three aspects: system architecture, communication model and interest mechanism. We present our middleware platform, HIVE, providing a variety of services such as data distribution, communication, event notification, etc. To achieve the reusability and interoperability of DVE applications, the interface specification of High Level Architecture (HLA) is employed as the reference. HIVE also contains the back-ends, which the middleware services depend upon. On HIVE, users can develop scalable DVE applications easily and quickly, concentrating on not the detail of distribution but the application logic. Finally an experimental demo on HIVE is given.