Abstract: In order to improve microcapsules dispersion and their effect on mechanical strength of composites, two coupling agents namely KH550 and KH560, were applied to modify microcapsules surface, and self-healing microcapsules dispersion in Glass-fiber reinforced plastic (GFRP) as well as their flexural performance were discussed. The results showed that after KH560 treatment, microcapsules dispersion improvement in GFRP reaches to 64.7%, which is better than KH550 treated microcapsules. However, flexural stress of the self-healing GFRP where microcapsules are treated by coupling agent is decreased. According to SEM observations, the interface between microcapsules and epoxy bonds well.