Benzophenone macromolecular photoinitiator and preparation method thereof

The invention relates to a preparation method of benzophenone macromolecular photoinitiator. The benzophenone macromolecular photoinitiator is a compound with the structural formula (I) shown in the specifications, wherein carboxylic ester substituent groups of benzophenone can be 2-position carboxylic ester substituent groups or 3-position carboxylic ester substituent groups or 4-position carboxylic ester substituent groups, each R1 and each R2 are independently selected from hydrogen, optionally substituted alkyl groups and optionally substituted aryl groups, n is an integer from 1 to 6, and L is residues of polyhydric alcohols. The preparation method has the advantages that reaction conditions are mild, operation is easy, the yield is high, and the cost is low; the preparation method is suitable for industrial production.