The hybrid locomotion system is a hotspot in mobile robot research. This paper firstly gives a brief review of the achievements accomplished in wheel-leg hybrid mobile platform, and the structural characters. Based on the spherical gear mechanism, a new mobile platform with wheel-leg hybrid mechanism is put forward. The wheel-leg mechanism has a novel character, that is, the wheel mode and the leg mode can be fused not only in structure but also in their function. As a result, the mobile platform has three mobile modes: independent wheel mode, independent leg mode and wheel-leg-fusion mode. The mobile platform can realize several mobile poses such as straight moving, sloping moving, turning in a smaller radius and even turning-in-place. The current design was testified by the results of simulation using virtual prototype technology and experiments based on the wheel-leg-system and the mobile platform physical prototype.