Abstract: Nitrogen and phosphorus in sediments play an important role in marine biogeochemical cycle. In order to study its potential function in matter cycling, the best conditions for simultaneous determination of nitrogen and phosphorus in natural grainy sediments were developed based on a series of experiments. Inorganic nitrogen and inorganic phosphorus were determined after extracted by 0. 1 mol/L HCl. Total nitrogen and total phosphorus were determined after being extracted by NaOH-K2S208 solution. The method has been used in the study on geochemical characteristics of nitrogen and phosphorus in sediments from Jiaozhou Bay. The results indicate that organic nitrogen occupies 50% - 70% of total nitrogen and organic phosphorus accounts for less than 40% of total phosphorus. Similar to other regions, the contents of inorganic nitrogen and inorganic phosphorus in surface sediments of Jiaozhou Bay increase with depth, while tend to be stable or little change in sub-surface sediments. In reverse, the contents of organic nitrogen and organic phosphorus decrease with depth. All the results indicate that the method for simultaneous determination of nitrogen and phosphorus in natural grainy sediments provides the advantages of simplicity, good accuracy and precision. The method can be used in study on ecological function of nitrogen and phosphorus and ecological toxicology of excessive nitrogen and phosphorus in sediments.