Abstract: A study was done on temperature rise, decarboxylation and the composition change of rosin under microwave irradiation for the first time.The results showed that rosin can be heated by microwave irradiating to cause temperature rise and isomerization, but not to cause ecarboxylation.The speed of rosin temperature rise was greatly influenced by the power of microwave irradiation but less influenced by granule size of rosin.These properties are beneficial to various sterification of rosin under microwave irradiation.