The novel sulfonic acid functionalized resorcinol-furaldehyde has been synthesized from resorcinol-furaldehyde and hydroxyethylsulfonic acid. The novel solid acid owned the high acidity of 4.5 mmol/g and the catalytic activities were investigated through the transesterification of rapeseed oil. The results showed that the novel solid acid was very efficient for the biodiesel synthesis with the high yield for the high water content rapeseed oil. Both the free fatty acid and triglyceride could be efficiently transformed to the biodiesel products and the rapeseed oil with high acidity also could be transformed to the products with high yields. (C) 2012 Elsevier Ltd. All rights reserved.