In Ulysses, there is a whole repertoire of linguistic inventiveness, creativity and play in the form of new words and odd constructions, which calls for our close reading. Lexical Inventiveness, as I argue, best characterizes Joyce’s lexical revolution in which both creativity and playfulness of language are fully stressed. To have a better understanding of them, this chapter is to investigate special conversions, unusual compounds and comic word-play by means of classification and comparison. Our studies show: (1) Joyce’s defamiliarized lexis is more motivated than arbitrary as he made the best use of the accepted lexical resources; (2) As for various word formations, we find that Joyce’s verb conversion follows fairly well the word-formation rules, his compounds deviate a lot from the rules and his jumbled compounds are, in its true sense, what Bakhtin calls “linguistic carnivalization”; (3) Semantically, neologisms, though fleeting, are terse, lively, exciting, expressive, and above all true to life. (4) Perfect truth was perfect language.” (French, 1982). The point with his linguistic inventiveness is to make full use of the visual and auditory textures of words, including their musical nature, and to increase the expressive power of literary language, and thus to achieve the special artistic effects of “defamiliarization” by increasing the difficulty of reading and lengthening their time of perception, and it is in grappling with linguistic deviation, creativity and indeterminateness that lies much of the pleasure of reading Ulysses. So Joyce’s linguistic inventiveness is part of his artistic ingenuity in fiction and calls for further studies.