This product is a further improvement and development of hydrolyzed polyacrylonitrile-ammonium salt (NH4-HPAN), overcoming the shortcomings of hydrolyzed polyacrylonitrile-ammonium salt in terms of poor salt and calcium resistance. Simultaneously, it further reduces the dynamic shear force and viscosity of drilling mud during the drilling process. Under the same conditions, compared with hydrolyzed polyacrylonitrile-ammonium salt, the filtrate loss of freshwater drilling fluid can be reduced by approximately 8%, and the filtrate loss of brine drilling fluid can be reduced by approximately 15%, with a significant reduction in apparent viscosity. This product has good compatibility and can be used in combination with commonly used treatment agents, exhibiting both filtrate loss reduction and viscosity reduction effects in freshwater, brine, and positively charged drilling fluids.