A complex mechanism of the reaction of diglycidylamine (DGA)-based epoxides with primary amines is described and the kinetic model is developed. The reaction mechanism involves the addition of amine, etherification, and also formation of small cycles and anionic homopolymerization of the epoxide compound including transfer and termination. The polymer structure was theoretically described by distribution of structural fragments determined using the kinetic model. Simulation of the structure evolution during the DGA-aniline reaction at varying molar ratios of reagents and dilution of the system was performed. The effect of the reaction conditions on the distribution of structural fragments, such as branching units and cyclic structures, was determined.