The dispersion status of flame retardants in polymer matrix greatly influences the performance of the flame retardant materials. Realizing ultra-fine and even dispersion of flame retardants is a challenge for researchers on most occasions. In this paper, an efficient method was employed to achieve ultra-fine dispersion of a nitrogen flame retardant, melamine cyanurate (MCA) in epoxy resin (EP) composites. Different from conventional means, in which MCA powder (synthesized in water, then dried and pulverized to powder) is added into EP glue solution, and then the flame retardant glue is coated on glass fabrics, and finally dried and compressed to laminated boards, here MCA is synthesized in a good solvent of EP. Without drying or pulverization processes like commercial MCA, EP pre-polymer is directly added to the synthesized MCA suspension to obtain the flame retardant glue. In this way, MCA can keep perfect dispersion in the glue. Although the following coating and compression involve the remove of the solvent, the EP molecular chains can effectively retard the aggregation of the flame retardant particles. Eventually, ultra-fine dispersion of MCA can be achieved in the cured resin. Compared with the conventional addition system easily resulting in MCA aggregates, the highly dispersed flame retardant system exhibits much better stability of the flame retardant suspension glue, and remarkably improved the flame retardance and mechanical properties. This work was kindly supported by the National Natural Foundation of China (No. 51473095) and State Key Laboratory of Polymer Materials Engineering (No. sklpme2014-3-11).