The reaction of a hydroxyl radical with molecular hydrogen and the respiration in Camellia Japonica are used as examples for studying chemical reaction rate constants by the power-law transition state theory. In the first example, the rate constants are numerically obtained at different temperature and activation energies based on the Morse potential at the potential well and improved potential energy surface 5 (I5B) at the saddle point respectively, and the relationship between the rate constants and the power-law parameter is plotted as well. In the second one, especially, the power-law parameter presents an abrupt change at temperature 290 K around, which may be explained that the Camellia Japonica is the ombrophyte, and the activity of biological enzyme reaches the maximum at this temperature. This theory allows accordance with experimental values by a power-law parameter. It is found that the values of the power-law parameter in both examples deviate from 1 but not too much and lie in the 0–1 range and proved that power-law transition state theory shows a good agreement with experiments.