The emotional aspect of autobiographical memories (AMs) is associated with self-related processing, which plays an important role in mental health. However, the emotional consistency dimension of AMs and its neural underpinnings remain largely unexplored. Twenty-five healthy participants were involved in this study. Participants were first asked to recall important AMs and assess the emotional ratings of each AM. Four weeks later, they were asked to retrieve the details of both positive and negative AMs during functional magnetic resonance imaging (fMRI) scanning. Behavioral results showed that the emotional valence of negative memories changed more strongly than positive memories over time (i.e., lower consistency). fMRI data showed that the activation level of the precuneus was positively correlated with self-rating valence consistency in the positive AM condition. Additionally, the precuneus connected to a key region of the self-referential network, the medial prefrontal cortex, in both the positive and negative AM conditions. Finally, the precuneus showed stronger connections with the inferior parietal lobule when comparing the positive with the negative AM conditions. Our results suggest that the precuneus is a key area of emotional consistency in positive AMs; this brain area may be involved in the maintenance of a positive self-image by strengthening positive AMs.