The weight balance calculation of the electric multiple units (EMUs)has effects on the train safety. In this paper the weight balance evaluation indexes of the EMUs were analyzed; the structure of the commonly-seen Bo-Bo shaft type EMUs was studied and a three-dimensional mathematical model for the vehicle was estab- lished. The rigid force balance principle and the torque balance principle were adopted for static analysis, and the calculation formulas of vehicle gravity center, axle load and axle load difference, wheel weight and wheel weight difference were derived. Then, the weight balance calculation software was developed for the EMUs based on the C# language of the Visual Studio 2010 platform and the SQL Server 2008 database. And the correctness of the software calculation results was verified by comparing the calculation results of the software with the mea- sured data. The proposed software can not only realize the weight balance calculation of the EMUs, but also manage all the vehicle data and improve the utilization rate of the data of the vehicle parts. Meanwhile, it will also be of reference for the tool development of other rail vehicles.