The velocity of vulcameter torque change during the vulcanization of natural rubber consists of two increasing and decreasing stages. The vulcanization process in the stage of velocity increasing is not a simple reaction, and can be expressed in an equation of In(M-H - M-t) = InA - K-I(t -t(0))(alpha), which is different from the famous equation of V-ut = - (aK(3)/K-4)In[(K(2)e(Klt) - K(1)e(K2t)) /(K-2 - K-1)] deduced by Coran, the value of K-1(1/alpha) in the former can be used as a rate constant to calculate the value of activation energy (E-3) according to the Arrhenius equation. The vulcanization process in the stage of velocity decreasing consists of two first-order reactions, and can be expressed in a kinetic equation of In(M-H - M-t) = InB - K(t - t(dis)). The time (t(p)) at which the torque change reaches to the maximum velocity (V-m) is corresponding to the time (t(dis)) suggested by Coran. (C) 2003 Wiley Periodicals, Inc.