Abstract: The structure and components of A-stage benzoguanamine-formaldehyde resins obtained in the conditions of various feed ratios and reaction times are identified by chemical analysis of formaldehyde contents in the resins, determination of M_n with VPO, and assignment of H-NMR spectra. It is proved that the resins are a series of methylol derivatives of benzoguanamine. The molecular species in the resins are datermined quantitatively with high-speed liquid chromatographic technique.