Abstract: In order to improve the layer structure of montmorillonite，cetylt rimethyl ammonium bromide (CTAB) and octedacy trimethyl ammonium chloride (OTAC) were used as organic intercalating cations to modify sodium montmorillonite. The effects of modification by the type and amount of organic cation added，reaction temperature，and pH were investigated，and the samples were systemically characterized with XRD，FTIR，TGA，SEM and TEM. The results showed that OTAC had a better intercalating effect than CTAB. It was found that a reaction temperature of 80℃ and low pH favored intercalation，and the best intercalating effect was observed when the amount of organic cation added was twice the cation exchange capacity (CEC). Under the above reaction conditions，ordered and high layer spacing organic nano-montmorillonite was successfully obtained，with a basal spacing of 4.12 nm and even exfoliated parts of silicate layer .