Contrastive focus, conveyed by prosodic cues, marks important information. Studies have shown that 6-year-olds learning English and Japanese can use contrastive focus during online sentence comprehension: focus used in a "contrastive context" facilitates the identification of a target referent (speeding up processing), whereas focus used inappropriately in a "noncontrastive context" misleads listeners to predict an incorrect referent, hindering the identification process (Ito et al., 2012, 2014). In Mandarin Chinese, the mapping between prosodic form and contrastive focus is less transparent, potentially delaying the acquisition of contrastive focus. This study assessed the online processing of contrastive focus by 196 Mandarin-speaking 4-10-year-olds and 34 adults in China, using the visual world paradigm. Stimuli contained a target NP in a mini discourse, with focus being used in "contrastive" (Experiment 1) versus "Noncontrastive" contexts (Experiment 2). Experiment 1 showed that the "appropriate" use of prosodic form for contrastive focus facilitated the identification of a target referent for 7-10-year-olds and adults, though not younger children. Experiment 2 showed that the "inappropriate" use of prosodic form for contrastive focus slowed the identification process only for 10-year-olds and adults. Thus, whereas 7-10-year-olds are sensitive to prosodic form for contrastive focus, only 10-year-olds use it as a primary cue to predict an upcoming referent like adults. The acquisition of contrastive focus in Mandarin is therefore a gradual process, with children showing sensitivity to contrastive focus during the early school years, and developing adult-like form-function mapping between prosody and focus until the end of primary school.