When light waves are scattered by a medium, the far-field optical properties including the spectral intensity, spectral coherence degree and spectral polarization degree, are closely related with the structure of the scattering medium. In recent years, much progress has been made in the research of weak scattering of light waves. On one hand, researchers have extended the scatterers to various scattering media, including the anisotropic medium, semisoft boundary medium, ellipsoidal medium, etc. On the other hand, the incident light waves are generalized to some commonly used light beams, such as the stochastic electromagnetic light wave, pulsed beam of the plane wave, non-uniform beam, etc. We introduce the main results of the research on weak scattering of light waves, including the spectral shift, spectral coherence, equivalence theory, reciprocity relation, inverse scattering, etc.