In order to screen strains from a bidirectional fermentation of Monascus and Dendrobium nobile and study the antioxidant activity of mycoplasm from a bidirectional fermentation medicine, three antioxidative modes in vitro, ABTS free radical scavenging, DPPH free radical scavenging, and inhibiting lipid peroxidation, were compared. Results showed that Vc group had higher ABTS and DPPH scavenging ratios compared to bidiretional ferment products, Monascus ferment products and Dendrobium nobile, while its anti-lipoperoxidation inhibition ratio was lower than those from the bidiretional fermentation medicinal mycoplasm of the two strains（P<0.01. The bidirectional fermentation medicinal mycoplasm from two?Monascus strains and Dendrobium nobile had a higher antioxidant activity compared to individual Monascus ferment products and Dendrobium nobile. In three modes in vitro, the two-way fermentation medicinal mycoplasm of strain GZUM-123 had the highest inhibiting lipid peroxidation with an increase of 30.09% (P<0.01). The study can provide a foundation for the development of a new bidirectional fermentation.