The relationship between the rate of enthalpy change of a chemical reaction and the formation rates of its constituents is derived, and then transformation equations for the thermokinetics of single-substrate enzyme-catalyzed reactions are deduced, and the validity and prerequisite of application of the chemical amplification of enthalpy changes to thermokinetic investigations are proved. A reduced-extent method is applied to thermokinetic studies of enzyme-catalyzed reactions, and then a reduced-extent equation for the kinetics and a mathematical model for the thermokinetics of the single-substrate enzyme-catalyzed reaction are suggested. According to this model, the kinetic parameters and molar enthalpy can be calculated simultaneously with the data from a single thermogram. Three enzymatic reaction systems have been investigated with a heat conduction calorimeter, and the thermokinetic research method in this paper is discussed in detail.