his paper is concerned with the fuel economy of a mini car with power split automatic transmission (PSAT) by means of simulation. Firstly, a PSAT prototype is developed featured with high efficiency by power split. Secondly, mathematic models of PSAT, based on the PSAT scheme and experiment on the prototype, is established and embedded into the simulation software NREL’s Advanced Vehicle Simulator (ADVISOR) to carry out the whole vehicle fuel economy simulation. Thirdly, fuel economy comparison between vehicle with PSAT and traditional mechanical transmission is present, after fuel economy simulation under different driving cycle. Finally, approach to the energy save scheme of PSAT and matching between PSAT and the whole vehicle is discussed which builds up a good foundation for future optimization on control strategy of PSAT.