This research work intended to study some important operational parameters on the photocatalytic activity of a new type of poly(methyl methacrylate) (PMMA)/IL-TiO2 nanocomposite, prepared by microemulsion method. For the first step, it is confirmed that the prepared nanocomposite has a significant effect on photodecomposition of the Trypan Blue (TB), as an anionic hydrophilic azo dye, and good antibacterial activity against Bacillus spp., as Gram positive bacteria, under visible light. After that, the operational parameters such as TiO2 content in photocatalyst, the thickness of the nanocomposite film, visible light intensity, and pH of the solution have been studied. In order to have a precise study on the photocatalytic performance of the prepared nanocomposite, the hydroxyl radical dosage in photocatalytic experiments and oxidative stress in the antibacterial experiment have been measured. This strategy was performed to show the extreme effect of TiO2 dosage on the photocatalytic activity of the nanocomposite.