Phorate is a highly toxic organophosphate pesticide used commonly in most of the developing countries. These pesticides are commonly washed away and mixed up in the water bodies leading to reduction in water quality and fatal consequences in the aquatic system. The application of nanoscale particles in pollution control is an emerging technology. It is considered more efficient because of its low cost and simplicity. The present study has been planned to investigate the photocatalytic action of chemically synthesized zinc oxide nanoparticles. The results showed that phorate was rapidly degraded by zinc oxide nanoparticles under solar light and the physico chemical properties of the water sample before and after treatment were studied. Maximum degradation of phorate zinc oxide nanoparticles were obtained after 120 minutes, which was measured photometrically at 350nm.