Abstract: The phase structures of hyperbranched epoxy resin/bisphenol A epoxy resin (EHBP-n /DGEBA) curing systems were studied by optical microscope. The relationship between the morphologies and mechanical properties of EHBP-n/DGEBA cured products was discussed. The results showed that the compatibility of the cured products was improved with the increase of EHBP-n mass fraction and the decrease of epoxy equivalent. The larger the particle size in the microstructure of the cured products was, the better the mechanical properties were. The curing process of 9%EHBP-12/DGEBA (the mass fraction of EHBP-12: 9%) was observed and the formation mechanism of homogeneous structure was proposed. The in-situ strengthening and toughening mechanism of hyperbranched polymer was confirmed. The curing kinetics of EHBP-n/DGEBA was studied by Differential Scanning Calorimetry (DSC), and the element distribution of the cured product was analyzed by Mapping. It further showed that EHBP-n had good compatibility with DGEBA, and it was a non-phase separation system after curing.