Abstract: The surface-charges of cells are very important to study the vital characteristic of cells.Common methods only measure the changes of cell electrophoresis mobility (EPM) instead of the quantity of cell surface-charges.In order to measure the surface-charges of cells,a novel method to measure the surface-charges of cells by means of optical tweezers and electrophoresis in a microchannel was designed.With this method,the quantity of the electric charge of yeast cells was measured about 10-10℃.Experimental results prove that this method can be used to measure the changes of cell surface-charges.A lab-onchip (LOC) for measuring the surface-charge of cells might be developed after improving this measuring system.