Synthesis of Magnesium oxide (MgO) nanoparticles and zinc deposited magnesium oxide (Zn/MgO) nanoparticles was carried out using hydrothermal and deposition-precipitation method with the variation of 1-Propanol (organic solvent) concentration, sodium hydroxide and urea concentration. The nanoparticles were characterized by using FTIR, TGA, SEM-EDX, TEM and XRD. The photocatalytic efficiency of MgO and Zn/MgO nanoparticles was studied by degradation of 2,4,6-trinitrophenol (TNP), which is highly acute and toxic and causes skin and eyes diseases, liver malfunction and tumor formation. Photodegradation of TNP was carried out under UV irradiation and confirmed by using HPLC and GC-MS. MgO and Zn/MgO nanoparticles that were synthesized by using urea showed higher firstorder rate constant (k) value and percentage degradation as compared to nanoparticles that were synthesized using NaOH. It was observed that the concentration of solvent has direct relation with the k value of degradation of TNP.