Abstract: By using the contrast between ***yiwei*** ‘falsely think’ and ***juede*** ‘think’ in Mandarin, the present study reports two experiments including a gold medal task examining children’s understanding of verb factivity, and a truth-value judgment task testing children’s understanding of belief-reporting sentences to investigate children’s acquisition of the syntax, semantics, and pragmatics of belief-reporting language. Results show that four-year-old Mandarin-speaking children are sensitive to the semantics and syntax of mental verbs. Their difficulty in understanding belief-reporting sentences is pragmatic in nature. When the saliency of beliefs is strengthened in the context, children are able to understand the belief reports. The strong non-factive ***yiwei*** in Mandarin can provide zoom-lens to remind children that others’ false-beliefs are under discussion in the complement.