The novel carbon-based strong acid catalyst has been synthesized through the simple heat treatment of 2-hydroxyethylsulfonic acid and starch. The novel solid acid owned the high acidity of 2.6 mmol/g, much higher than that of the traditional solid acids such as Nafion and Amberlyst-15 (0.8 mmol/g). The catalytic activities of the novel carbon-based acid were investigated through the acetalization reactions. The results showed that the novel solid acid was very efficient for the reactions with high yields. The high acidity and catalytic activities made the novel solid acid hold great potential for the green chemical processes.