Degradation of dyes is a standard method to check the photocatalytic activity of any type of photo catalyst. Photo catalytic degradation materials such as ZnO, ZnS have been studied because of high photochemical reactivity, H2 production, hexagonal wurtzite / zinc blende structure and nontoxic nature. In this report the photo catalytic property of ZnO and ZnS nanoparticles separately and the combination of ZnO-ZnS (ZnO0.5S0.5 ) and the copper dopped ZnO-ZnS nanoparticles, which are synthesised by simple solvothermal method are investigated. Methyl orange (MO) is taken as a model organic compound. The percentage of degradation is calculated. It is found that the % of degradation is improved in the combined ZnO-ZnS nanoparticles system while comparing to the individual ZnO , ZnS nanoparticles. However the copper doped ZnO-ZnS nanoparticles show much degradation percentage comparing to the others. These results indicate that the copper doped ZnO-ZnS nanoparticles can be a good choice for the treatment of organic waste-water in future