Akidolestes cifellii Li and Luo, 2006 (NIGPAS 139281A, B) is a new symmetrodont mammal with complete postcranial skeleton discovered in Yixian Fromation, Lower Creatacous, Liaoning province, China. It has been diagnosed as a member of family spalacotheriidae included in superfamily spalacotheroidea. The spalacotheriidae is a monophyletic group; characteristic by the reversed triangular molar. It is the close relative to extant therians (metatherians and eutherians), with a lot of primitive features. Akidolestes differs from zhangheotheriids in having much broader coronoid process of dentary and more acute angled molars. The skeletal anatomical and morphological comparative study indicates that the evolution of Akidolestes is mosaic pattern combing the primitive and the derived skeletal features. Akidolestes probably shares both terrestrial and arboreal locomotory adaptation, but it is not specialized in either aspects.