Barley $eta$-glucan was subjected to chemical modification and the anticoagulant activity of the derivative was investigated. The barley $eta$-glucan was successfully sulfated, showing the degree of substitution calculated by elemental analysis of 0.40. In addition, the Fourier transform infrared (FT-IR) spectra of the derivative confirmed the sulfation, which generated two new absorption bands at 1,250/cm (S=O) and 810/cm (C-O-S) compared to the native. Specially, the anticoagulant activity of barley $eta$-glucan was created by sulfation, which increased in a concentration-dependent manner. This result demonstrated that the incorporation of sulfate groups into the $eta$-glucan structure added a blood clotting prevention effect.