Natural materials have become an important direction for the research and development of environmentally friendly drilling fluid treatment agents due to their advantages of easy degradation， environmental friendliness， rich sources， and low prices. Based on natural pomelo peel， amide and sulfonic acid groups were introduced through chemical synthesis to form a modified pomelo peel fluid loss reducer that can meet the requirements of green， safe， and efficient drilling in high-temperature strata， and its temperature resistance， inhibition， and salt and calcium resistance performances were evaluated. Pomelo peels are rich in active ingredients such as plant phenols and polysaccharides. The modified pomelo peels have strong temperature resistance and a filter loss reduction rate exceeding 70% at 150℃. The rolling recovery experiment results show that at a dosage of 0.3%， its inhibitory effect is better than KCl. The anti-pollution experiment shows that the modified pomelo peel fluid loss additive has good salt and calcium resistance. At a dosage of 0.3%， it can keep the filter loss below 10 mL in fresh water base mud， salt water base mud， and saturated salt water base mud. When the CaCl₂ content is 3%， the filter loss reduction rate reaches 82.22%. The modified pomelo peels have significant fluid loss reduction properties， providing new technical ideas for the development of environmentally friendly drilling fluid treatment agents.