The invention discloses a macromolecular bifunctional amino ketone photoinitiator and a preparation method thereof. Single amino ketone photoinitiators are combined with one another by using di-secondary amine, so that a molecular weight is doubled and the defects of easy volatilization, easy migration, smell and the like caused by a small molecular weight are overcome; simultaneously, the numberof introduced invalid groups is small and the performance of the initiator is not lowered obviously; moreover, a molecular chain is longer and the problem of poor compatibility is solved. The invention also discloses the application of the macromolecular bifunctional amino ketone photoinitiator in a polymerization reaction. The photoinitiator has high initiating efficiency, high performance in various aspects and wide application prospect and can fully replace a micromolecular amino ketone photoinitiator.