Urea-formaldehyde microcapsule was produced by means of one step in-site polymerization.Optical microscope, scanning electron microscope and laser scanning confocal microscope (fluorescence tagged microcapsule shell) were used to analyze the size, shell thickness and structure of the microcapsule.The mechanical properties of the microcapsule was tested and analyzed by nano indentation test.The results showed that the dispersed and integrated microcapsules of 100 μm in diameter and 10 μm in shell thickness were produced with 45% core content.Young’s modulus of the microcapsule was a little lower than that of epoxy resin.When damage occurred in the epoxy resin matrix, the crack could rupture the microcapsule and release the repairing agent.