This study investigated the effects of presentation unit and presentation duration on the comprehension for reading Chinese text on the small screen of a mobile phone in three different contexts (seated, walking on a treadmill, and walking through an outdoor course). Thirty readers participated in this study. In each of the three contexts, participants read eight passages that were dynamically presented with various combinations of presentation units (word-by-word or single line) and presentation durations (171, 213, 240, and 308 milliseconds per character (msC-1)). Results showed that presentation unit and presentation duration significantly affected reading comprehension, and interactions between factors were also significant. When the presentation unit was word-by-word, no significant difference in reading comprehension was observed under different presentation durations. However, when the presentation unit was a single line, reading comprehension deteriorated with the shortest presentation duration of 171 msC-1. With regard to context, participants had a higher mean reading comprehension score in the seated context than in ambulatory contexts, but the difference was not significant. Recommendations for appropriate dynamic display design for presenting Chinese characters on the screen of mobile devices based on the results of objective measures are discussed.