Cardanol based novolac resin was prepared. Cardanol based novolac-type phenolic resin was prepared under microwave irradiation by the reaction of cardanol ( C ) and formaldehyde ( F ) with mole ratio 1:0.8 of C/F using tricarboxylic acid as catalyst. Analogical synthesize have been done using conventional heating for the comparison of the methods. The methylolation of cardanol was confirmed by Fourier-transform infra-red (FTIR) spectroscopic analysis and a reaction mechanism was proposed. The numberaverage molecular weight was found by gel permeation chromatographic (GPC) technique. On the basis of the calculated value of kinetic chain length, the structure of the novolac-type phenolic resin was proposed. The main advantage of the process is twofold reduction of reaction time of the process carried at microwave reactors in comparison to the conventional heating.