本文基于瞬态光电流模型和多色谐波脉冲叠加形成的类锯齿形电场，研究了频率比为1：2：m（m为正整数）的飞秒三色谐波脉冲诱导空气等离子体产生太赫兹波的情况。结果表明，在空气被饱和电离且电子密度达到相同最大值的情况下，对于相同数量的谐波脉冲，当合成脉冲包络中的电场形状更接近锯齿形且更不对称时，太赫兹波的转换效率并不总是更高。此外，研究了采用频率比为1：2：3和1：2：4的飞秒三色谐波脉冲的特定波长组合方案增强太赫兹波的产生。对于这些特定的波长组合方案，可以在常用频率比为1：2的双色光脉冲方案基础上仅添加一组光参量放大器就能实现。我们的研究将有助于获得强太赫兹波源，并为实验操作提供指导。

The generation of terahertz waves from air-plasma induced by femtosecond three-color harmonic pulses with a frequency ratio of 1:2:m (m is a positive integer), based on the transient photocurrent model and the sawtooth-like electric field formed via multi-color harmonic pulses superposition, has been theoretically investigated. It can be seen that when the air is saturated ionized and the electron density reaches the same maximum, for the same number of harmonic pulses, terahertz conversion efficiency is not always higher when the electric field shape in the composed pulse envelope is closer to a sawtooth waveform and more asymmetric. Besides, the specific wavelength combination schemes of femtosecond three-color harmonic pulses with the frequency ratios of 1:2:3 and 1:2:4 have also been simulated, which can significantly enhance the generation of terahertz waves, and are realized by adding only a set of optical parametric amplifiers on the basis of the conventional two-color laser pulse case at the frequency ratio of 1:2. Our study will be helpful to obtain intense terahertz sources and provide guidance for experimental operations.