The Nanocomposites consist of graphene oxide (GO) nanosheets and Magnesium oxide (MnO2), with a weight ratio of 1:1 to the synthesized GO /MnO2. The synthesized samples were characterized using FT-IR, SEM. The adsorption of Congo red (CR) dye from aqueous solution onto GO/MnO2 NCs as adsorbent using the batch method were investigated under different laboratory conditions such as contact time, dose of GO/MnO2, temperature and initial concentration of CR dye. Adsorption isotherms are used to test adsorption data for Langmuir, Freundlich, Dubinin, and Temkin, because it is suitable to Temkin isotherm. Thermodynamic functions (Δ ºH, Δ ºG, ΔºS ) of the adsorption were calculated, which show the adsorption endothermic process and the Δ ºG values were negative, meaning that the adsorption occurred spontaneously. The ΔºS values were positive, meaning that the movement of the dye molecules is unrestricted. The Kinetic data were proportional to -pseudo-second order. We also investigate the photodegradation of CRdyeon GO/MnO2 under different conditions (with and without sunlight, GO/MnO2 and light source), we calculated Photodegradation percent and kinetic photodegradation. The bestcondition for photodegradation was GO/MnO2NCs + CR + O2 gas + Vis lamplight.