We have studied on a nanoparticle precipitator using thermophoretic force by temperature gradient. The deposition time of nanoparticles onto a substrate was computed by theoretical analysis and CFD methods, respectively. We analyzed the deposition time by two methods, and we notice of a particle motion and tendency. Also, we carried out experiments using simple apparatus and got the SEM images collected particles. As a result, we predicted a particle motion in the precipitator using theoretical equation and CFD and we designed the precipitator using design variables by this study.