The　role　of　guide　sign　to　inform　road　user　about　the　information　of　network　is　important.　How　to　design　and　locate　guide　sign　to　increase　traffic　operation　efficiency　is　a　key　point　for　traffic　engineers.　Driving　simulator　is　useful　devised　to　study　guide　sign　in　the　process　and　system　control.　For　the　purpose　of　studying　guide　signs　using　the　tool　of　driving　simulator,　guide　sign＇s　validity　in　driving　simulator　was　studied.　Results　of　this　experiment　are　the　foundation　of　further　study　on　guide　sign.　Simulator　calibration　procedure　for　guide　sign　was　set　up　in　this　study.　Legibility　distance　as　measure　of　performance　was　used　to　evaluate　the　validity　of　guide　sign　in　driving　simulator.　Thirty　two　participants　were　recruited.　Results　indicated　legibility　distance　and　speed　were　inversely　related　with　the　method　of　data　mining.　Legibility　distance　and　text　height　of　guide　sign　were　positive　related.　When　speed　is　20km/h,　30km/h,　40km/h,　magnifying　power　of　text　height　is　4.3,　4.1,　3.8,　while　guide　signs　are　absolute　validity　in　driving　simulator.