The own-age bias refers to a phenomenon that people had higher face recognition performance on their own-age faces than other-age faces. The mainstream explanations for this phenomenon are the holistic processing hypothesis and the experience-based hypothesis. The holistic processing hypothesis proposes that (1) people have stronger holistic processing on their own-age faces than other-age faces, and (2) holistic processing is positively correlated with the ability of face recognition. Such that, the stronger holistic processing results in better performance of own-age face recognition. The experience-based hypothesis holds that the primary reason for the own-age bias is the extensive, recent experience that people acquired from contact with their own-age peers. However, the explanation of holistic processing on own-age bias provides less information about how this holistic processing works. Besides, both own-age bias and holistic processing can be affected by face orientation. Kuefner et al. (2008) found that adults had higher performance on their own-age face than other-age face when faces were presented upright but not inverted. Pellicano and Rhodes (2003) found that participants adopted the holistic processing to the upright face, but not to the inverted face. Rossion (2008) proposed the perceptual field hypothesis to explore the nature of holistic processing of face. This hypothesis preliminarily supported by Van Belle, Lefevre, & Rossion (2015) who developed a gaze-contingent morphing approach. However, it is still uncertain that whether the size of perceptual field can be an index as the strength of holistic processing. Also, when using the perceptual field size to evaluate the holistic processing, how does the own-age bias effect change? By using the gaze-contingent morphing approach and the inverted face paradigm, we tried to test two hypotheses: (1) If the perceptual field size can be an index to evaluate holistic processing, then participants’ perceptual field size should be larger when they processed upright face than inverted face; (2) If perceptual filed size can be an index of holistic processing and the holistic processing hypothesis can explain the own-age bias effect, then participants should have larger perceptual field size on their own-age faces than other-age faces when the faces are presented upright but not inverted. In two experiments, the present study found that: (1) Both adults and children had larger size of perceptual field when they recognized upright face than inverted face; (2) When faces were presented upright, adults, but not children, had large size of perceptual field on their own-age faces than other-age faces. But this effect was not evident in inverted face condition. These results indicated that perceptual field size can be an index as the holistic processing of face. The own-age bias of holistic processing can be affected by the face orientation. Compared with previous paradigms, perceptual field-based gaze-contingent morphing approach reveals how the own-age bias of holistic processing works. When participants gaze a specific feature on their own-age faces, other identities outside the specific feature will affect the perception to the specific feature, which is supported by large size of perceptual filed; but when participants recognize the feature of the other-age faces, their perceptual field is restricted to this feature — a small size of perceptual field.