Abstract: This paper investigates the relationship between syntax and semantics of Chinese epistemic and alethic modals along the line of Cartographic Approach.There are controversies concerning syntactic properties of modals, such as keneng and yinggai, which denotes possibility and necessity respectively.Our investigation reveals that both of the modals can function as epistemic and alethic modals.The former denotes subjective judgment, while the latter denotes objective description.Following Cinque's Cartographic Approach (1999;2006), the epistemic modal is positioned in the CP layer, while the alethic modal in the TP layer.The syntactic analysis of various modal constructions shows that the initial noun in the epistemic modal construction is a topic, the initial noun in the alethic modal construction is a subject.Our study demonstrates that the Cartographic Approach is effective in accounting for the mapping mechanism between the syntax and semantics of modals.