Road　random　roughness　was　simulated　by　using　inverse　fast　Fourier　transform(IFFT)　in　time　domain,　a　half-vehicle　dynamics　model　was　established,　the　effects　of　road　grade,　vehicle　velocity,　loading　capacity　and　vehicle　parameters　on　vehicle　dynamic　load　were　studied　by　Runge-Kutta　method,　and　the　rules　of　vehicle　dynamic　load　caused　by　road　roughness　were　studied.　Simulation　result　indicates　that　vehicle　dynamic　load　increases　obviously　with　the　intensification　of　road　roughness;　vehicle　dynamic　load　and　the　dynamic　load　coefficient　increase　with　the　increase　of　vehicle　speed,　their　peak　values　appear　nearby　inherent　frequency;　dynamic　load　coefficient　decreases　and　vehicle　dynamic　load　increases　with　the　increase　of　loading　capacity,　so　overload　phenomena　is　strictly　limited;　increasing　tire　stiffness　and　decreasing　suspension　damping　can　lead　to　the　increase　of　vehicle　dynamic　load　and　dynamic　load　coefficient,　so　the　use　of　high　pressure　tire　should　be　limited　and　the　selection　of　suspension　damping　should　be　reasonable.