Abstarct: In recent years, bismuth oxyhalides, BiOX (X = I, Br, Cl), have attracted much attention from researchers due to their potential photocatalytic application as well as the removal of pollutants. Researches show that among bismuth oxyhalides, bismuth oxybromide (BiOBr) has a unique photocatalytic property. However, in BiOBr photocatalyst, the rate of electron and hole recombination is high, which prevents the optical performance of this photocatalyst. The aim of this dissertation is to improve the photocatalytic properties of bismuth oxybromide due to the high rate of electron and hole pair recombination created in this material and thus reduce the electron-hole recombination rate, create retrievability, improve its physical, chemical, and optical properties, and finally, a significant increase in photocatalytic performance. In this study, a set of modified nanoparticles and nanocomposites baxsed on bismuth oxybromide were synthesized and were used to evaluate the photocatalytic activity in the degradation of organic pollutants. Prepared samples include bismuth oxybromide (BiOBr) nanoparticles, tin porphyrin-sensitized bismuth oxybromide (BiOBr/SnTCPP), (BiOBr/Sn-itTCPP), (BiOBr/Sn-iTCPP), Bismuth oxybromide doped with silver and porphyrin (BiOBr/Ag), BiOBr/Ag@TCPP), and (BiOBr/Ag@SnTCPP), bismuth oxybromide and polyaniline (PANI/BiOBr) nanocomposite, a ternary nanocomposite consisting of bismuth oxychloride and bismuth oxide bromide and polyaniline (BiOBr/BiOCl/PANI (BP)), synthesis of a ternary nanocomposite with porphyrin sensitizers (BiOBr/BiOCl/PANI@TCPP) and porphyrin from tin (BiOBr/BiOCl/PANI@SnTCPP), synthesis of ternary nanocomposites doped with silver and porphyrin (BP/Ag), (BP/Ag@TCPP), (BP/Ag@SnTCPP). Samples prepared were identified using X-ray diffraction pattern (XRD), Transmission electron microscopy (TEM), Field emission scanning electron microscope (FE-SEM), Map of the dispersion of elements on the surface (Map), X-ray energy diffraction spectroscopy (EDS), Photoluminescence spectroscopy (PL), UV-Vis electron spectra and Raman spectroscopy. The efficiency and photocatalytic activity of the prepared samples were evaluated in the photodegradation of organic pollutants such as methyl orange, rhodamine B, and 2, 4-dichlorophenol. According to the results, it was observed that all synthesized nanocomposites have higher photocatalytic performance than pure bismuth oxybromide. Furthermore, the possible photocatalytic mechanism on nanocomposites was also discussed through radicals and holes trapping experiments. The heterostructure improved photocatalytic activity dramatically, which greatly promoted the migration rate of the photoinduced electrons besides limiting the recombination of photogenerated electron-hole pairs. In addition, the stability of photocatalysts during several stages of recycling was investigated and it was shown that nanocomposites are very stable and can be reused without significantly reducing the degradation efficiency of photocatalysts. The photocurrent response BiOBr, BiOBi/BiOC/PANI, BiOBi/BiOCl/PANI@TCPP and BiOBi/BiOCl/PANI@SnTCPP nanocomposites were investiged. The photocurrent measurements demonstrate that the BiOBi/BiOCl/PANI@SnTCPP nanocomposite has higher photoactivity. Moreover, sensitization of the BiOBr with silver and porphyrin is successfully capable to develop a new type of photocatalyst system for disinfection of bacteria in visible light irradiation.