Epoxy resins used in reactors are prone to cracking and failure due to mechanical vibration, thermal stress, and ultraviolet radiation. Improving their resistance to damage is important to extend the service life of reactors. This investigation develops a self-healing imidazole-cured epoxy resin for reactors using epoxy microcapsules and amine microcapsules prepared by electrospraying-interfacial polymerization (ES-IP) microencapsulation technique. Firstly, this investigation studies the feasibility of using double nozzles for simultaneous spraying to improve the preparation of small-sized microcapsules. After successful synthesis, the healing performance of self-healing imidazole-cured epoxy based on the microencapsulated epoxy-amine chemistry was studied, focusing on the influence of the ratio, concentration, and size of the two microcapsules on the healing efficiency, and further exploring the thermal stability of the self-healing performance. The addition of microcapsules to the mechanical properties was also investigated. Results show that the double-nozzle technique can prepare microcapsules with controllable sizes (20~200 μm). The self-healing imidazole-cured epoxy exhibits high self-healing performance, reaching 100% at the optimal ratio with 10.0 wt% 50~100 μm microcapsules. Although the added microcapsules reduce the tensile strength of the material, they improve its high-temperature aging resistance. The above investigation is significant for developing self-healing fiber-reinforced epoxy-based composite materials for reactors.