Abstract: In recent years, a new kind of ungrammatical bei passive expression, such as bei zisha and bei lihun, has emerged. Literature review shows that current explanations of this neo-bei constructional utterance meaning can be broadly categorized into two types: grammatical and pragmatic. Grammatical approaches focus on examining the intra-linguistic information but tend to neglect extra-linguistic factors such as context, thereby failing to account for the underdetermined interpretation of its constructional meaning in use. Pragmatic approaches generally emphasize the importance of extra-linguistic pragmatic inference, but pay insufficient attention to the conventional information in grammar, which serves a crucial meaning-making resource in communication. Therefore, this paper aims to offer an novel account of neo-bei constructional utterance meaning construal mechanism based on grammar-pragmatics interaction or integration. It finds that neo-bei construction is essentially an under-specified construction whose encoded conventional grammatical meaning and conventional pragmatic meaning are both underdetermined. The interpretation of a speaker’s utterance meaning conveyed via this neo-bei construction in use relies on a constructional merger representation of grammatical conventional passiveness, pragmatic conventional affectedness and pragmatic inference.