Ensuring the signal integrity even under pico-second switching-time in PCBs (printed circuit boards) as well as in VLSI chips is one of the most important goals in a PCB design. To achieve the goal, we propose a novel methodology of the PCB trace design in which the traces are regarded as segmental-transmission-lines of individual impedances. Also, the impedances are optimized by minimizing signal distortions due to multiple reflections in the transmission lines through genetic algorithms. Our design system shows excellent experimental results which achieves almost ideal signal wave forms without any signal distortion.