Abstract: In order to settle the issues of poor rheology for drilling fluids in Antarctica, it is important to develop an agent that can availably address these challenges. For this reason, a rheological regulator (HSCN) of drilling fluid was synthesized by modifying montmorillonite with composite modifiers (DODMAC and CPL). The structure of HSCN was characterized by X-ray diffraction, contact angle, infrared spectroscopy and scanning electron microscopy. And HSCN properties were also evaluated by experiments such as colloidal rate, rheology, viscosity-temperature characteristics and corrosion test. Finally, the mechanism of HSCN was investigated. 2% HSCN can enhance the improvement rate of yield point for drilling fluid at −55 °C by 167%, and the colloidal rate of drilling fluid is 90.4% after 24 h. The corrosion of the three rubbers is weak, with a maximum mass increase of only 0.014 g and a maximum outside diameter increase of 0.04 cm. The mechanism study shows that the staggered lapping between HSCN lamellar units forms an infinitely extended reticular structure. The structure is mainly formed by the electrostatic attraction between HSCN particles, hydrogen bonding, physical adsorption and entanglement between the long carbon chains in HSCN. The formation of this structure can effectively enhance the rheology properties of drilling fluids. This research gives a direction for the investigation of drilling fluids suitable for Antarctic conditions, which is greatly sense for accelerating the efficient exploitation of oil and gas in Antarctica.