The anisotropy of photocurrent induced by two-photon absorption in [110]-cut nearly-intrinsic crystal silicon sample is investigated. The anisotropy coefficient of third-order nonlinear susceptibility of Si at wavelength of 1.3 μm is measured to be -0.25, and the ratio of χxxxx to χxxyy is 2.4. The independent element χxxxx is consequently obtained to be about 1.49×10-19 m2/V2 based on the previously observed result of χxxyy.