Abstract: Abstract: In this study, the mixed-species biofilm on coconut and stainless steel mesh formed by Streptococcus thermophilus and Lactobacillus bulgaricus was observed using scanning electron microscope, then the preliminary study on fermentation performance and resistance of mixed-species biofilm on stainless steel mesh was conducted. The results showed that S. thermophilus and L. bulgaricus could form typical mixed-species biofilm on coconut and stainless steel mesh, and the bacterial density change curves of broth fermented by mixed-species boifilm on stainless steel mesh was similar with S-shaped growth curve，while the lag phase and logarithmic phase was not obvious; The pH value of broth fermented by mixed-species boifilm decreased in the early stages and then stabilized in the later stages, finally pH close to 4.0. In addition, the mixed-species boifilm has stronger resistance than free bacteria,and could release high concentrations of bacteria stably in 15 days.