Abstract: In order to investigate the effects of defatting process on volatile compounds in yak beef stock, the volatile compounds of beef stock prepared with and without defatting process from yak were determined through gas chromatography-mass spectrometry (GC-MS) . It was found that defatting process decreased aldehydes and esters in beef stock by 34. 78 % and 16. 65 % respectively, and increased ketones and hydrocarbons by 33.37% and 17.93% respectively. While hexanal, heptanal and octanal from lipid oxidation products was significantly decreased by 1.28%, 7.44% and 5.81% (p <0.05) respectively through defatting process, and benzothiazole from Maillard reaction products was highly significantly decreased by 1. 01 % (p <0.01) . There were 19 volatile compounds only detected in beef stock with defatting process, such as decane and 2, 3-heptadione (top 2 relative content, with 5.85% and 2.21%, respectively) . It was showed that defatting process had a significant effect on volatile compounds in yak beef stock, and some volatiles could be detected through defatting process.