The torsional vibration model of the vehiclular powertrain in a multishaft and complex branch structure is established and further studies are carried out on the method of calculation of torsional vibration problems. The purpose is to supply a theoretical basis for the design of powertrain components and for a further study on their characteristics. Adopting the matrix method, torsional vibrations are calculated. An interfacefriendly torsional vibration analysis software has been developed with Matlab and its GUI toolbox, suitable for the calculation of both free and forced vibrations. Its validation is completed in this paper. The software can also be used for complex powertrains of ships.