Abstract: To further improve temperature resistance and filtration reduction of lignin derivatives in drilling fluids, ammonia -oxidized lignin was prepared with the lignosulphonates. The influences of reaction conditions, such as temperature, pH, and content of oxidizer and ammoniation agent, on the performance of ammonia-oxidized lignin in drilling fluids were investigated. The results showed that the product not only can enhance dynamic sheer force and reduce filtration at room temperature, but also can reduce dynamic sheer force and filtration at high temperature. After aging for 16 hours at 180 ℃, the ammonia-oxidized lignin enhanced the fluid loss reduction rate to 11.4%. Compared with lignosulphonates, the ammonia-oxidized lignin has weaker function of reducing the dynamic sheer force but higher temperature resistance.