Abstract: In order to study the effect of biopolymer(xanthan gum) on the flexural strength and fracture properties of clay, different contents of xanthan gum were added into the clay, and a single-edge notched beam was made for three-point bending test.The fracture behavior of clay beams under different water content and different xanthan gum content was analyzed.The results showed that the water content has a significant negative correlation with the flexural strength and fracture characteristic parameters of clay beams under low water content.The addition of xanthan gum can significantly improve the flexural strength, fracture performance and the maximum displacement before fracturing of clay beams under dry conditions, and make the clay beams change from brittle failure to ductile failure.The improvement of these properties is positively correlated with the content of xanthan gum.Finally, based on the moisture content and xanthan gum content, a nonlinear expression of flexural strength and fracture parameters of clay beams was established.The fitting results confirm that the method has high fitting accuracy.