The previous literature on working memory (WM) has indicated that verbal materials are dominantly retained in phonological representations, whereas other linguistic information (e.g., orthography, semantics) only contributes to verbal WM minimally, if not negligibly. Although accumulating evidence has suggested that multiple linguistic components jointly support verbal WM, the visual/orthographic contribution has rarely been addressed in alphabetic languages, possibly due to the difficulty of dissociating the effects of word forms from the effects of their pronunciations in relatively shallow orthography. In the present study, we examined whether the orthographic representations of Chinese characters support the retention of verbal materials in this language of deep orthography. In Experiments 1a and 2, we independently manipulated the phonological and orthographic similarity of horizontal and vertical characters, respectively, and found that participants' accuracy of probed serial recall was reduced by both similar pronunciations and shared phonetic radicals in the to-be-remembered stimuli. Moreover, Experiment 1b showed that only the effect of phonological, but not that of orthographic, similarity was affected by concurrent articulatory suppression. Taken together, the present results indicate the indispensable contribution of orthographic representations to verbal WM of Chinese characters, and suggest that the linguistic characteristics of a specific language not only determine long-term linguistic-processing mechanisms, but also delineate the organization of verbal WM for that language.