Abstract: The linear heating apparatus formed by resistance wire was designed to investigate the formation of the microstructures of the cured epoxy resin. The network of the gel states was analyzed by means of SEM. And 3D Temperature Testing Instrument was employed to survey the temperature distributions in the curing epoxy resin system heated by resistance wire. The results show that the microstructures of the cured resin, heated by linear resistance wire, exhibit the formation of the gel state of the cured resin heated homogeneously. It indicates that the temperatures of the curing resin are greatly affected by the content of the curing agent. These are of great value in understanding the effects of microstructure development and temperature distribution on the composites manufacturing process.