To investigate the chemical kinetics of tanshinone IIA in different conditions quantitatively and calculate the chemical kinetic parameters and equations in order to find out the major factors affecting the stability of tanshinone IIA.The kinetic line was obtained by setting the ln (C(t)/C0) as ordinate and making time as abscissa. The slope of the kinetic line was the reaction constant of tanshinone IIA in such condition. The t1/2 was calculated by the equation t1/2 = 0. 692/K.The influences of initial concentration, pH value, temperature and light on stability of tanshinone IIA in solutions were carried out, respectively. The results suggested the degradation of tanshinone IIA in solutions fitted the pseudo-first-order reaction. The chemical kinetics parameters including rates constant and half time of degradation in different conditions were obtained by the means of ln (C(t)/C0) versus reaction time. The activation energy of tanshinone IIA in solutions were also available from the calculation of rate constants under different temperature according to the Arrhenius equation and was 82. 74 kJ/mol.Tanshinone IIA is unstable in the high temperature and light conditions, and is prone to degradation, this may be the main reason for its decrease in the whole process of extraction, concentration, granulation, drying and ending product of Danshen prescription.