Abstract: In the process of shock formation, it was found that the tendency to saturation exists for harmonics with the increasing of foundamental sound pressure level (L_p1).When L_p1 < 153 dB, the relation between the sound pressure amplitude of m-th harmonic p_m and that of fundamental P₁ is about p_m~p₁^m.When the fundamental changes 1 dB,the m-th harmonic will increase m dB. The fundamental and all its harmonics start their transition toward saturation at about the same time during the increas of excitation.The relation of p_m~p₁^m tends to p_m~p₁. The trend of saturation can be divided into three regions in frequency domain:Ⅰ.linear region; Ⅱ. alteration region, and Ⅲ. shock region. When L_p1 > 160 dB, the shock is formed. These results are useful for further theoretical work.