Abstract: This study aimed at screening lactic acid bacteria with excellent fermentation and aroma production performance from local traditional fermented dairy products. Traditional Tibetan yak yogurts samples were collected from the Aba Tibetan and Qiang Autonomous Prefecture,Sichuan province. Lactic acid bacteria were selected through genetic stability,fermentation time and sensory evaluation,and together with SPME-GC-MS for flavor. Totally 5 strains with excellent fermentation performance were screened from 26 yogurt samples,their fermentation time were 4.5~7.5 h,titration acidity were 74.0~78.4 °T,and sensory evaluation results were good. Results of SPME-GC-MS showed that the contents of key flavor substances such as acetaldehyde(1.13 mg/L)and diacetyl(4.90 mg/L)produced by strain AB1504 was the highest. The conclusion of this study was that Streptococcus thermophiles AB1504 screened from traditional Tibetan yak yogurts had nice fermentation performance and flavor,it has the potential for commercial application.