The affordances of networked media lead users to leave abundant digital traces across the internet. Through users" active behaviors, these traces converge to form their digital identities in cyberspace, reflecting the control of the "self" over its "avatar." However, when the subjectivity of digital identity is absent, the construction of that identity ceases to be directed by the "self." Based on this, our study focuses on the construction mechanism of digital identity in the absence of the subject, specifically that of the deceased. Using in-depth interviews combined with grounded theory, we find that the dissemination process of online mourning is itself the process of constructing the digital avatar of the deceased. This process is driven synergistically by four types of actors: media representation acts as the initial catalyst, sparking broad social attention and discussion. Subsequently, participation by netizens, involvement by relatives, and the deceased"s prior digital self-presentation collectively contribute not only to the widespread dissemination of online mourning but also to the formation of a social consensus regarding the deceased"s digital identity.