The characterization of the degree of crosslinking of methyl methacrylate-divinyl-benzene (MMA-DVB) copolymer was studied by means of pyrolysis chromatography. Linear relationships were obtained between (hEVB/hm-DVB)average and the degree of crosslinking (in the range of 4-24%) when different samples of DVB were used as raw material. Refinement of the data made it possible to determine the degree of cross-linking directly from the averages chromatographic peak height ratio mentioned above and the composition of DVB used. The mechanism of the pyrolysis of the copolymer was also discussed and a comparatively satisfactory explanation was proposed.