The invention discloses a heat-resistant epoxy resin curing modifying agent, which is prepared from the following ingredients in parts by weight: 100 parts of N-substituted phenyl maleimide with carboxylic groups, 50 to 150 parts of vinyl monomers and 20 to 80 parts of maleic anhydride. The preparation method comprises the following steps of adding N-substituted phenyl maleimide with carboxylic groups and maleic anhydride into a container; then, adding a solvent; performing heating reaction in an electric heating stirring reaction kettle; after the stirring dissolution, slowing adding the vinyl monomers into the reaction kettle; after the complete reaction, performing cooling; pouring the materials into water for separation and drying; obtaining the heat-resistant epoxy resin curing modifying agent. The obtained epoxy resin curing modifying agent can be used as a co-curing agent of the epoxy resin to be used, and can also be used as a heat-resistant modifying agent at the same time. The heat-resistant epoxy resin curing modifying agent provided by the invention has the advantages that the preparation process is simple; the operation is convenient; the reaction condition is mild; the heat-resistant epoxy resin curing modifying agent is favorable for industrial production; the heat-resistant epoxy resin curing modifying agent can be used in the field of electrics and electronics.