The influence of carbon fibre on the curing kinetics of the prepolymer based on bisphenol A cyanurate and epoxy resin has been studied using infra-red spectroscopy. It was found that the curing process of the prepolymer is very complicated. It is shown that in curing the prepolymer a number of the sequential transformations of one ring structure into others occurs. An introduction of the carbon fibre (CF) of two types, original CF and modified CF (MCF) containing phosphate groups, affects strongly the prepolymer curing. Both CF and MCF accelerate the conversion rate of epoxy groups. In the case of cyanate groups, the former has practically no effect on their conversion whereas the latter decelerates strongly this process. In the present paper the influence of CF on the mechanism of the copolymer formation is considered.