The invention relates to a kind of thermosetting composition, a curing film and a filter. The invention provides a kind of thermosetting composition and the curing film thereof that can be used as filter protection film with flatness, heat resistance, chemical resistance, adhesiveness, hardness, electrical reliability and transparency. A kind of thermosetting composition is characterized in containing epoxy compound (A), epoxy compound (B) and a curing agent (C), wherein the epoxy compound (A) is expressed by formula (1), and the avenue value of n is 0.2-1.0; the epoxy compound (B) is obtained through polymerizing or copolymerizing more than 1 polymerizable unsaturated compound that takes glycidyl methacrylate as an essential ingredient. When epoxy equivalent is smaller than 200g/eq and number-average molecular weight less than 10 thousand, the curing agent (C) is selected from polycarboxylic acid, anhydride of polycarboxylic acid and thermal decomposition ester of polycarboxylic acid. The above thermosetting
