A dataset of two drifters in South China Sea was analyzed, together with the MSLA, Ekman drift, and mean sea surface height. It was shown that the velocity of the drifters is consistent with the geostrophic current derived from MSLA. Several regression models, with an independent variable of sea surface geostrophic current, were set up to simulate the real trajectories of drifters. Experiments on the two drifters showed that the model, with independent variables of sea surface geostrophic current, Ekman drift, and mean circulation, has the best efficiency of simulating real trajectories. The simulated trajectories match the real trajectories perfectly. By analyzing the simulated velocities, it was shown that:①In the middle of eddies, the drifter was controlled mainly by the sea surface geostrophic current;②In the edge of eddies, the Ekman drift played an important role in driving the drifter into (out of) eddies;③The mean circulation made the drifters flow correctly in some regions.