The reactions between Laccase (extracted from China lacquer of Rhus vernicifera) and various substrates (3,4-Dihydroxybenzaldehyde, Guaiacol, Pyrogallol, Gallic acid) have been studied using LKB-2107 batch microcalorimetry system. Based on calorimetry, a new method has been proposed. Laccase activity and the Michaelis constant K-m have been determined simultaneously by this method. The method is simple, sample-saving, and valid for a wider range of substrate concentrations. Furthermore, it can be extended for assaying other enzymes catalyzing reactions ...