We present the experimental study to realize a DNA separation chip using asymmetrically-switched nonuniform electric fields. The DNA separation chip redistributes DNA molecules within a specific area based on the size- and field-dependent nonlinearity of DNA drift velocity. The present chip is composed of a width variable channel to distribute nonuniform electric field, a DNA loading slit and a pair of electrodes to apply electric field. We focus on the design of DNA separation chips with identifying the nonlinearity of DNA drift velocity using three different DNA molecules (11.1kbp, 15.6kbp, and 48.5kbp) in the chips. It is demonstrated that different size of DNA shows different net migration in different direction under the asymmetrically-switched nonuniform electric field.