A numerical model of an ethanol droplet system containing ZnO nanoparticles was developed using finite element analysis. The spatial, voltage, and frequency dependence of positive dielectrophoretic trapping mechanism was analyzed with all the AC electrokinetic forces incorporated into our calculation. The AC electrokinetic forces were analyzed individually, compared, and analyzed collectively. The characteristic behavior of each phenomenon was demonstrated, and dielectrophoresis was shown to be the dominant force near the edges of electrodes. Through time evolution study of the particle concentration in the collective analysis, we calculated optimal values of voltage and frequency at which the dielectrophoretic trapping mechanism is the most effective. This versatility of our numerical model promises its potential application in parameter optimization.