The importance and necessity of emulating the federation load during simulating was analyzed firstly.Then,the special federation load emulation tool,federation load simulator (FLS),was designed and implemented,by which all of the vital essential characteristics of a simulation could be tested,e.g.the amount of federates,the joint/resigned speed of federate,the amount of object instances,the registered/deleted speed of instance in one single program,etc..The applications proved that FLS could provide a convenient,effective and adjustable simulation load testing environment during the procedure of run-time infrastructure(RTI)and interrelated tool federates researching,developing and performance testing.Furthermore,the FLS utilized all kinds of resources with high efficiency.