Abstract: With the development of computer hardware, network, and software technology, and also with the development of social requirements, distributed interactive simulation applications which involve massive complex scene and large quantity of simulation entity objects put high demand on simulation object management capability and scene rendering ability. There are two problems in the existing HLA-based distributed interactive simulation applications. One is the fact that the timeliness of scene simulations with massive complex scene are bad. The other is that the management of simulation entity object and the management of rendering object are separate. In order to solve the above problems, a unified object model consisting of heterogenous scene graph tree, action list and universal access interface, is presented, realizing the efficient organization and unified management of simulation entity object and rendering object. The unified object model builds a bridge for high efficient data exchange between HLA-based simulation platform and parallel rendering platform, reducing the development workload of integration between them, and supporting the real-time rendering of massive complex scene and large quantity of simulation entity object to help to enhance the timeliness of scene simulation. The unified object model is a common method for HLA-based simulation platform and parallel rendering platform. Finally, an experimental demo with analysis is given.