A coil pyrolyzer and processor-controlled gas chromatograph were used for analysis of rubber for compounding ratio of the single and blend rubber vlucanizates. Variables such as sample size, pyrolysis temperature, time allowed for pyrolysis, the column packing material, its length and programmable temperature for gas chromatography were examined to obtain optimum condition for application to NR, BR and SBR blends. By application fixed conditions, three kinds of standard curves were finally obtained from thirty samples of blend vulcanizates which were prepared in the pilot plant, NIRI. It is possible to determine rubber composition and their ratio in NR, BR and SBR products by pyrolysis.