Using dimer acid (DA) as raw material, DA diglycidyl ester (DADGE) was synthesized and used as reactive toughening agent to prepare paper‐based copper clad laminate (p‐CCL). The factors affecting the epoxy value of DADGE and the effect of the resin on the gelation time were studied. The effects of the epoxy value and the addition amount of DADGE on the solderleaching resistance, flammability, water absorption, bending strength, and impact strength of the p‐CCL were discussed. The results showed when the molar ratio of DA to ECH was 1:8 and the molar ratio of DA to sodium hydroxide was 1:1.6, the epoxy value of DADGE reached the maximum value of 0.23 mol/100 g. The DADGE can shorten the gelation time of the glue. The p‐CCL meets the performance of the IPC‐TM‐650 standard. And when the addition amount of DADGE is less than 12 wt %, the flammability of the p‐CCL reaches UL94V‐0 level. The p‐CCL prepared by adding 6 wt % of DADGE with 0.08 mol/100 g epoxy value has the best comprehensive performance, its toughness and rigid are comparable to those of p‐CCL with 12 wt % of commercially available high performance toughening agents and it has higher solderleaching resistance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47508.