In order to realize the rational utilization of waste, C/Fe3O4 was obtained by using biomass as the carbon source and prepared via one-step method, afterwards, a double conductive C/Fe3O4/Bi2O3 composite photocatalyst was further synthesized via solvothermal method. Due to the good double conductivity, the electrons in Bi2O3 could be transported to C/Fe3O4, which greatly inhibited the recombination of electron-hole pairs, it is worth noting that the double conductivity effectively blocked the reverse transfer of electrons to Bi2O3. Consequently, the photodegradation rate of C/Fe3O4/Bi2O3 composite photocatalyst reached 91%, which was much higher than that of pure Bi2O3. In addition, the mechanism exploration experiment showed that h+ was the main activity specie, meanwhile, the photocatalytic electron transfer mechanism was also investigated.