The thermal behaviour of aloe-emodin, chrysophanol and physcion and their kinetics have been investigated under non-isothermal conditions by means of differential thermal analysis (DTA) and thermogravimetry (TG). The thermal characteristics have been determined using the DTA and TG-DTG curves. The non-isothermal kinetic data were analyzed by means of the Achar method and the Madhusudanan-Krishnan-Ninan (MKN) method. The possible reaction mechanisms have been investigated by comparing the kinetic parameters. The kinetic equation for aloe-emodin, chrysophanol and physcion can be expressed as dα/dt=Aexp(-E/RT)1/3(1-α) [-ln(1-α)]-2. The activation energy E (kJ mol-1) of the three free anthraquinones are 78.09, 89.54, and 107.5 and their lnA/s-1 are 22.98, 36.85 and 43.60, respectively. The thermal behavior of aloe-emodin, chrysophanol and physcion and their kinetics have been investigated under non-isothermal conditions by means of differential thermal analysis (DTA) and thermogravimetry (TG). The thermal characteristics have been determined using the DTA and TG-DTG The non-isothermal kinetic data was analyzed by means of the Achar method and the Madhusudanan-Krishnan-Ninan (MKN) method. The possible reaction mechanisms have been investigated by comparing the kinetic parameters. The kinetic equation for aloe-emodin, chrysophanol and physcion can be expressed as dα / dt = Aexp (-E / RT) 1/3 (1 -α) [-ln (1- α)] - 2. The activation energy E (kJ mol- 1) of the three free anthraquinones are 78.09, 89.54, and 107.5 and their lnA / s-1 are 22.98, 36.85 and 43.60, respectively.