Abstract: High level architecture (HLA) is based on a single federation execution, and does not refer to the interoperability and reusability between heterogeneous RTIs and multi-federations. Presented in this paper is a software architecture based on bridge federate to interconnect heterogeneous RTIs and multi-federations. Then the design and implementation of RTIBridge, an interconnecting software of heterogeneous RTIs and multi-federations, are described. The typical procedures the bridge federate take when executing RTI services are analyzed. And then a heterogeneous RTIs and multi-federations development and execution process model is provided. Finally experiment results are given.