An epicyclic-type automatic transmission is a device which is connected from the engine to the driven wheels. A Lepelletier automatic transmission consists of a two-DOF epicyclic gear mechanism and a fundamental geared entity, which can provide more speed ratios. For the development of automatic transmission with eight or more speed ratios, an efficient design methodology is urgently needed and still not available. Therefore, the purpose of this article is to develop a systematic method for the design of Lepelletier automatic transmission. First, the features and requirements of the Lepelletier automatic transmissions are investigated and the corresponding design requirements are induced. Next, the theory of the analysis of speed ratios for Lepelletier automatic transmission is derived based on the concept of lever analogy. Then, the design theory of Lepelletier automatic transmission is developed based on the analysis theory. Finally, the complete atlas of six-speed and eight-speed Lepelletier automatic transmissions can be systematically synthesized from the data of three given speed ratios. In this article, the innovative and patentable six-speed and eight-speed Lepelletier automatic transmissions with the simplest structure have been. This proposed design method can also be applied to the development and design of ten-speed Lepelletier automatic transmissions.