Cordyceps sinensis is a kind of precious Chinese herbal medicine that is good for medical treatment and health care. The pharmacological characteristics of this kind of medicine is not based on a single or few kinds of chemical substances but on the whole constituted with all elements. In order to explore the pharmacological characteristics, this paper takes the Chinese herbal medicine, cordyceps sinensis as the whole, and the absorption peaks of the one-dimensional linear spectrum of the medicine as normal modes. The Hamiltonian of interaction between laser and cordyceps sinensis is modeled based on assuming the interaction intensity between modes and the size of the dipole moment resulting from laser irradiation. Then the two-dimensional third-order nonlinear laser spectra of the cordyceps sinensis are calculated. The theoretical spectra are adjusted with the experimental ones, thus the level structure, the coupling strength between each normal modes, and the dipole moment of each mode for the cordyceps sinensis can be obtained. This is a new method of the pharmacological researches for the valuable Chinese herbal medicine.