Industrial syngas contains a large amount of CO2, and the resource utilization of CO2 is of great significance to the current environmental improvement. The homoacetogenesis in the anaerobic fermentation process has two characteristics : autotrophic and heterotrophic. It can use CO2 and H2 to produce acetic acid, and can also degrade glucose to produce volatile fatty acids ( VFAs ). This study intends to use its autotrophic characteristics to explore its ability to convert CO2 into resources, and to explore the effects of headspace H2 / CO2 ratio, carbon source type and pH value on the synthesis of homoacetogenesis reaction products. The results showed that high pH value was conducive to the autotrophic reaction of homoacetogenic bacteria using H2 / CO2 mixed gas. When pH = 5 and H2 / CO2 = 3 : 1, the yield of VFAs ( including acetic acid, propionic acid and butyric acid ) was the highest, reaching 3369.89 mg / L, and the proportion of acetic acid was 76.1 %. When glucose and H2 / CO2 mixed gas were used as a common carbon source, the homoacetogenic bacteria would preferentially use glucose for heterotrophic reaction, and then the H2 / CO2 mixed gas began to be utilized.Significant analysis showed that there was a weak correlation between VFAs content and pH value, but a negative correlation with H2 / CO2, indicating that CO2 content had a greater impact on the autotrophic pathway of homoacetogens. In addition, this paper also established a BP neural network prediction model for homoacetogenic reaction, which can accurately predict the VFAs production of homoacetogenic bacteria with H2 / CO2 mixed gas as carbon source ( R2 = 0.96584 ).