Most of the HDD projects in Shanghai area are conducted in sandy soft soil formations, and different special requirements of mud property should be taken into consideration. However, because of the similar property of the commonly used compound synergistic commercial bentonite, it is difficult to adjust the most favorable property in accordance with every single engineering case. Therefore, the main design points of drilling mud property in such engineering environments are discussed, the mechanism of material addition is analyzed and some useful and practical material technologies for parameters of mud density, viscosity and shear as well as water loss volume are given in order to provide a reference method for mud application under similar engineering conditions.