The influence of auxiliary ingredients and their amounts on the yield of γ-aminobutyric acid (GABA) was investigated based on the single factor test of producing GABA with highland barley fermentated by monascus, and the orthogonal test L9(33). The optimal varieties and amounts of auxiliary ingredients, were obtained. The production condition was optimized. The results showed that the yield of GABA could be increased by adding auxiliary ingredients. The optimal medium formula of solid fermentation were as follows: 48% highland barley, 10% corn flour, 17% black bean flour, and 15% rice flour; the yield of GABA was approximately 24.62±0.18mg/100g after 8 days′ fermentation at 30℃.