Ultrafast third-Order nonlinear Optical responses of GeS2-Ga2S3-CdS glasses have been measured by using femtosexond time-resolved optical Kerr effect(OKE) technique at he wavelengths of 820nm and 640nm respectively.The experimental results show that GeS2-Ga2S3-CdSglasses have large femtosecond third-order optical nonlinear responses and their OKEsignals vary considerably with the composition.The relationship of structure-property is discussed by means of Raman spectroscopy analysis, suggesting that the tetrahedron unit[GeS4]or[GaS4] plays an important role in the ultrafast third-order nonlinear opticla response.Inaddition,the experimental results also revesl that the ultrafast third-order optical nonlinearity of these glasses does not obey the Miller rule.