Abstract: On the basis of single factor experiment,the technology of spirulina yoghurt fremented by Trbetan mushroom was optimized by response surface methodology,and high space-solid phase micro-extraction(HS-SPME)and gas chromatography-mass spectrometry(GC-MS)were adopted for qualitative and quantitative determination of volatile flavor substances in the yogourt. The results showed that,the optimum conditions for the fermentation were:9% spirulina extract,3% inoculum,14 h fermentation time,7% sucrose addition,and 28 ℃ fermentation temperature. The sensory quality score under the conditions was 88.1±0.32.Using the common yoghourt as a control,the fermentation of spirulina yoghourty contained 41 kinds of flavor substances,mainly composed of 6 kinds of aldehydes(43.68%)and 8 kinds of esters(26.83%),8 kinds of alcohols(11.18%),9 kinds of ketones(10.49%),and 7 kinds of acids(5.68%). Among them,12 kinds of flavor components such as p-methylbenzaldehyde,2,4-dimethylbenzaldehyde,ethyl lactate,and 2-heptanone were detected in both types of yogourt. In addition,Tibetan mushroom fermented spirulina yogourt contained 8 kinds of alcohols and 7 kinds of acids,each accounting for 11.18% and 5.68%,while ordinary plain yogurt contained 2 kinds of alcohols and 9 kinds of acids,accounting for 4.17% and 28.76%,respectively. Caused by the fermentation of Tibetan mushroom,the alcohol compounds increased and the acid compounds decreased,which made the new yoghourt product taste softer and give it a wine flavor.