Abstract: As a close-mold process, it is difficult to observe the mold filling and chemical reaction procedure in the RTM process. In this study, the reaction information in the mould was obtained using the dielectric analyzer for on-line monitoring. The resin reaction temperature and ionic conductivity under different mold temperatures were investigated. The influence of the fabric volume fraction on the composite permittivity was studied. And the ionic conductivity during the curing process was studied for different fabrics. The results show that the exothermic reaction increases the local temperature in the composite and a complex temperature gradient distribution was formed. In the case of high temperature and low fabric volume fraction, the ionic conductivity changes dramatically, which in turn has a significant influence on the resin curing process. The fabric type also affects the ionic conductivity, with a higher value for random mat reinforced composites than that of woven fabrics.