In the digital era, Digital Voice Assistants (DVAs) have become a significant channel for children to acquire knowledge. However, little is known about how the type of explanatory testimony influences children's epistemic trust in DVAs. This study employed a conflicting sources paradigm, manipulating both the type of explanatory testimony provided by DVAs (teleological explanations vs. mechanical explanations) and the conflict situations (non-conflict vs. low-conflict vs. high-conflict), to examine the epistemic trust and its developmental characteristics of 90 children aged 4-6 years in DVAs. Data were analyzed using Generalized Linear Mixed Models (GLMM). The results showed: (1) Children exhibited higher epistemic trust in DVAs providing teleological explanations. This trust preference showed significant age differences, compared to the 5-year-old and 6-year-old groups, the 4-year-olds demonstrated a stronger trust tendency towards teleological explanations. (2) In conflict situations, children's trust in the DVAs providing teleological explanations significantly decreased across all ages. Furthermore, the degree of conflict influenced children's epistemic trust, compared to high-conflict situations, in low-conflict situations, children were not only more willing to trust DVAs providing teleological explanations but also more inclined to revise their pre-existing beliefs. (3) Belief revision also exhibited significant age differences, 4-year-olds were more prone to revise their pre-existing beliefs, whereas 5- and 6-year-olds showed a stronger tendency to maintain their original beliefs. This study is the first to investigate the mechanisms and developmental patterns of children's epistemic trust in DVAs. It provides empirical evidence for evaluating the educational suitability of DVAs as informants for children and offers valuable insights for optimizing the effectiveness of children's interactive learning with DVAs.