The structure of carboxymethylcellulose/montmorillonite(CMC/MMT)nanocomposites was characterized by X-ray diffraction(XRD)，transmission electron microscope(TEM)and scanning electron microscope(SEM).The nanocomposites were prepared with a solution intercalation technique and the effects of mass ratio of carboxymethylcellulose to montmorillonite，reaction time and reaction temperature on adsorption capacity were investigated.The desorption properties were also investigated. Microscopic observation showed that carboxymethylcellulose intercalated into montmorillonite interlayer via destroying the crystalline structure of montmorillonite，and intercalated-exfoliated structure was formed in carboxymethylcellulose/montmorillonite nanocomposites.The maximum adsorption capacity of the nanocomposite for Congo red dye was as high as 50.42 mg·g-1 using the mass ratio of carboxymethylcellulose to montmorillonite of 1∶1 after being treated at 60℃ for 6 h.The desorption efficiency of the nanocomposite was 80.17% using desorption agent of 0.01 mol·L-1 NaOH after being treated by ultrasonic wave for 50 min.