The embodiment of the present invention is to provide a system for sorting biological particles in a liquid flow, such as a cell sorter, which comprises an optical mechanism emitting laser beam onto each of the biological particles to detect light therefrom, a controller determining a moving speed of each of the biological particles in the liquid flow in accordance with the light detected therefrom, and an electric charger charging each of the biological particles based upon the moving speed thereof. Therefore, the cell sorter according to the embodiment of the present invention can improve recovery rate and purity of the desired cell particles.