The meaning of "~Shitemoii" always correspond to "keyi" in Chinese, while in some cases, these two words defy semantic correspondence. Based on Meaning Expansion Network Model, this paper analyzes the semantic relations and meaning expansion process of "~shitemoii" and"keyi ". Through etymological studies and corpus analyses, this paper points out that "~shitemoii" is used to denote the meaning of "permission, concession, promise, intention, advice, possibility, courage, and regret" etc., the basic meaning of which is "permission". Compared with "~shitemoii" signifies a more inactive mood. Contrastively, the denotative meaning of "keyi" is "possibility", however, "keyi", with a larger scale of meaning including interpersonal modality, can also imply "ability，invitation, and order" etc.，which does not completely correspond to "~shitemoii".At last, this paper points out that when "keyi" and "~shitemoii" are used in their own coordinating structures like "keyi… ye(also)keyi"and"~shitemoii…~shitemoii", many of their derivative meanings are lost and they mainly refer to the meaning of "possibility" and "permission". This paper argues that the semantic non-correspondence of "~shitemoii" and "keyi" is caused by the different process of meaning expansion of each word.