研究了短脉冲强激光在欠稠密均匀等离子体中的传播，得出光场的演化方程和包络所满足的非线性方程，并用这些方程对光场在等离子体中激发的相对论谐波的饱和问题和光场传播的演化特性进行了分析． The propagation of a short pulse intense laser in an under-dense plasma was studied. The evolution equation of the light field and the nonlinear equations satisfied by the envelope were obtained, and the saturation problems of the relativistic harmonic waves excited by the plasma in the plasma field were studied by these equations And the evolution of light field propagation characteristics were analyzed.