In order to enhance the anti-crack and anti-scour property of cohesive clay, a series of evaporation, dry shrinkage cracking and anti-scour tests were carried out on xanthan gum composite cohesive clay mixed with sand of different contents. By measuring the moisture content of the sample and anti-scour coefficient of the soil, and quantitatively analyzing the development of surface crack of the soil with graphic analysis software, the internal water change law, anti-crack and anti-scour performance of the composite cohesive soil were studied. The results show that, with the addition of sand particles, the crack rate, crack width and scour damage degree of cohesive clay samples increase first and then decrease. When the sand content is 30%, the crack rate, crack width and scour damage degree of cohesive clay samples with or without xanthan gum are higher than those of other sand contents. When the sand content is about 50%, the xanthan gum colloid forms a stable structure with a certain strength with sand particles for xanthan gum composite silty clay, and its anti-scour performance is significantly improved.