Through a thermal treatment method, LiFe5O8 nanoparticles are prepared and by using situ polymerization method, reduced graphene oxide/lithium ferrite (RGO/LiFe5O8) nanocomposites with the ratios of 0.15, 0.20 and 0.25 are created. The structural and physical properties of prepared samples are analyzed by different techniques. By using degradation of methylene blue (MB), photocatalytic activity is investigated under visible light. The combination of LiFe5O8 nanoparticles with RGO causes the enhancement of photocatalytic activity in same conditions. Moreover, after five recycles, photocatalytic activity of RGO/LiFe5O8 does not change as compared to the photocatalytic activity of fresh catalyst, indicating the stability and reusability of RGO/LiFe5O8. Additionally, the antibacterial characteristics of studied samples were investigated against Staphylococcus aureus (S. aureus) as Gram- positive bacteria and Escherichia coli (E. coli) as a Gram- negative bacteria with inhibition zone and colony counting methods. According to obtained results, the pure LiFe5O8 do not have any antibacterial effect on S. aureus, and E. coli. RGO/LiFe5O8 nanocomposites with the maximum concentration of RGO have a greater antibacterial effect on S. aureus, and E. coli than LiFe5O8 nanoparticles and RGO/LiFe5O8 nanocomposites with lower RGO ratios.