In order to explore the metallogenetic substances, environment and ore-forming age of Sanchakou, Tuolahaigou and Dazaohuo nephrite deposits in NS-trending metallogenic belt of Qinghai, the authors conducted Ar-Ar dating and analysis of major elements, trace elements and rare earth elements (REE). Major elements analysis shows little change in all samples from three deposits, which is in accordance with theoretical value of tremolite. The content of rare-earth elements in all samples is generally lower (0.29×10^-6~40.72×10^-6), with moderately negative Eu anomalies (0.49~0.84). Except for green nephrite, the chondrite-normalized REE patterns of samples exhibit relative light REE (LREE) enrichment and right-declined REE distribution patterns, with (La/Yb)_N values ranging from 2.87 to 6.34. Green nephrite samples are characterized by the enrichment of heavy REE (HREE) in the left-declined REE distribution patterns, with (La/Yb)_N values ranging from 0.16 to 0.61. REE distribution curves of samples from Sanchakou and Tuolahaigou nephrite deposits are similar to the patterns of Nachitai basic gabbro, and yellow nephrite samples from Dazaohuo deposit in northern metallogenic belt are similar to monzonitic granite, whereas green nephrite samples are similar to plagiogranite. The results indicate the source of mineralization of different deposits. The change of the content of Ti and Al₂O₃ in the sample shows changes in metallogenic temperature and pressure. The ratios of Zr/Hf, Nb/Ta and Sr/Ba in viridite and yellow nephrite samples are significantly lower than those of other samples, indicating that the alkalinity of metallogenic environment was obviously enhanced. The Ar-Ar dating shows that ore-forming ages of three deposits (301.38~237.28 Ma) are between Late Devonian to Middle Triassic, later than the geological age of intrusive rocks. The results indicate that Qinghai nephrite was mainly formed in the Hercynian-Indochina period, corresponding to multiple mineralization processes.