The results of the femtosecond time-resolved optical Kerr at 820 nm in GeS2-In2S3 chalcogenide glasses indicate that the response time in GeS2-In2S3 glasses is subpicosecond, which is predominantly due to the distortion of the electron cloud. The value of chi (3) in 0.95GeS(2)-0.05In(2)S(3) glass is also as large as 2.7 x 10(-13) esu, and it reduces with the addition of In2S3, which may be ascribed to the microstructure evolution of GeS2-In2S3 glasses. It is deduced that the intrinsic [Ge(In)S-4] tetrahedral structure units that possess the high hyperpolarizability may do great contribution to the enhancement of third-order optical nonlinearity while [S3Ge-GeS3] ethane-like molecular units make no considerable contribution to that in femtosecond time scale. These GeS2-In2S3 and GeS2-In2S3-based chalcogenide glasses would be expected to be the promising materials for all-optical switching devices.