Effective hydrolysis of chitosan, the N-deacetylated product of chitin, remains challenging. Here, we report acid-promoted hydrolysis of chitosan in imidazolium based ionic liquids with good total reducing sugars (TRS) yield under mild conditions. TRS yield reached over 60% in the presence of about 6.0wt% concentrated hydrochloric acid at 100°C within 7h. Kinetic modeling of a typical experimental data set suggested that the hydrolysis most likely followed a consecutive first-order reaction sequence, where k1 and k2, the rate constants for TRS formation and degradation, were determined to be 0.01372 and 0.00015min−1, respectively. Our method may be useful to explore new applications of natural chitin resources.