Methylglucoside (MEG) has been used in the water-based mud with fine montmorillonite (MMT) swelling inhibition, but it still has such shortages as large concentration and low thermostability. In this work, carboxymethyl glucoside (CMG) was synthesized with glucose and sodium chloroacetate and used as swelling inhibitor. The inhibition of CMG against clay swelling was investigated by MMT linear expansion test, mud ball immersing test and bentonite inhibition test. The results showed that the CMG has a good inhibition to the hydration swelling and dispersion of MMT. Under lower concentrations, the linear expansion rate of MMT in CMG solution is much lower than that of MEG, and the hydration expansion degree of the mud ball in the CMG solution was significantly inhibited. The characterizations of physicalchemical properties of particle, analysized by thermogravimetric analysis and scanning electron microscopy revealed that CMG plays a great role in preventing water from absorbing and keeps MMT in large particle size.