The invention provides a self-hydrogen-supplying benzophenone photo-initiator and a preparation method thereof. The photo-initiator has a structural formula represented by the formula (I). The photo-initiator can greatly reduce the mobility during the benzophenone application process while does not reduce the initiation activity at the same time. The yellowing phenomenon is improved. More important, the molecular structure of the photo-initiator comprises a tertiary amine structure, and the tertiary amine group can be used as the H donator for active functional groups, so the photo-initiator can be initiated without adding an active amine additive, and belongs to the self-hydrogen-supplying hydrogen-abstraction type photo-initiator. Furthermore, the photo-initiator can be easily dissolved in various kinds of resins especially the oligomer of resins, and is a very good substitute of BP.