Abstract: In the inertial confinement fusion (ICF),to achieve optimum fuel compression,the laser beams must irradiate the target uniformly,requiring excellent beam quality.In this paper,using the modeling of transient stimulated rotational Raman scattering (SRRS),the SRRS of high-power ultraviolet laser beams in long air path has been studied.The threshold condition for the SRRS,the effect of diffraction and hot spots on laser beam quality has been anal yzed.As a result,the effect of diffraction on threshold is very small,but it makes the beam quality decrease.The hot spots not only decrease the threshold con dition but also drop the beam quality.