This study investigated, by think-aloud protocols, the noticing process of incidental vocabulary acquisition in reading tasks, and the effects of time pressure and context identification on incidental acquisition. Four types of noticing process were discovered, i.e. “comprehension difficulty–contextual meaning,” “comprehension difficulty removed–usage,” “vocabulary recurrence–contextual meaning,” and “vocabulary recurrence–usage.” Results also showed: (1) comprehension difficulty in reading was an effective trigger for noticing on new vocabulary items; (2) the effect of the noticing process on incidental vocabulary acquisition was positive, but the type difference of noticing process seemed invalid to the acquisition; (3) the main effect of time pressure and the interaction of time pressure and context identification were not significant, while the main effect of context identification was remarkably significant – the more similar contextual clues were to those in the reading, the better the learners would identify the meaning of the new vocabulary items.