Abstract: Capillary electrophoresis of DNA fragments (from 80bp to 584bp) in replaceable linear polyacrylamide (LPA) solution was investigated using laser induced fluorescence detection. The fluorescence dye was Ethidium Bromide (EB). When the electric field strength was changed from 100V/cm to 375V/cm, the variation curves about current, mobility, signal intensity, width at half-height and the resolution were obtained. The nonlinearity Parameter of experimental current and electric field strength are 0.99944 and 0.99876 with 4%LPA and 6%LPA respectively; it shows that linear relationships are good. The mobility is varied as a complex function of fragment size and electric field; the electrophoresis mobility depends on the applied electric field strength, the concentration of gel matrix and the size of the fragment. The electric field strength is effect on the signal intensity little, but the gel matrix concentration affects the peak width so it affects signal intensity. The broadening is less and signal intensity is higher with 4% LPA than with 6% LPA. It shows 4% LPA is more suitable for separating DNA samples which the fragment size 600bp. The electric field strength affects resolution complicatedly; the resolution cannot be increased only increasing electric field strength. In order to increase the resolution, the optimum electric field strengths are 125V/cm. The analysis above is very useful for experiment.