Cuprous oxide nanoparticles at high concentration (up to 0.3M) were successfully synthesized by modified polyol process. The redispersion stability could be controlled by optimizing various conditions like polymer concentration, temperature, reductant, and catalyst. Reductant and catalyst play a crucial rule in redispersion of cuprous nanoparticles. Under poor conditions, particles grow to larger sizes due to aggregation of nanoparticles. This modified polyol process allows monodispersed cuprous oxide to be obtained on gram scale in a single reaction and make possible a high synthetic yield of more than 80%.