Abstract: The epoxy resin-urea-formaldehyde (E-51-UF) microcapsules were synthesized by one-step in-situ polymerization with UF resin as the shell and E-51 as the core material. The structure, surface morphology, heat resistance and particle size distribution of E-51-UF microcapsules were characterized by FTIR, SEM, TG and particle size analyzer. The E-51-UF@2-methylimidazole (2-MI) composite microcapsules were prepared by blending E-51-UF microcapsules as the core and 2-MI as the shell. The E-51-UF@2-MI composite microcapsules were filled in the epoxy resin matrix and E-51-UF@2-MI microcapsules/E-51 composite samples were prepared for the tensile, bending and trapezoidal double cantilever beam (TDCB). The electronic universal testing machine was used to test the properties of the samples. The effects of the mass fraction of E-51-UF@2-MI composite microcapsules on the mechanical properties and self-healing properties of E-51-UF@2-MI microcapsules/E-51 composites were analyzed. The results show that the prepared E-51-UF microcapsules have a regular spherical structure with an average particle size of 130 μm and a heat resistant temperature of 364℃. When the mass fraction of E-51-UF@2-MI microcapsules is 10wt%, the tensile strength of E-51-UF@2-MI composite microcapsules/E-51 composites reaches a maximum of 31.17 MPa, the bending strength is 66.77 MPa and the maximum self-healing ratio is 90.1%.