Tri-dimensional substation simulation is still under the risks of long-term modeling， and has difficulty in reusing model. This paper introduces a solution of tri-dimensional simulation platform based on extensible object collection. Objects in the collection have tri-dimensional， electrical， operational and data-interface characteristics. They can be reused or restructured to form new objects with different characteristics. With network and database technology， the tri-dimensional platform is functionally interactive with the bi-dimensional simulation platform in the training system. Since functions of various equipment can be modified at the object level， a new simulation function can be easily realized only with minor changes.