Abstract: A two-dimensional,nonhydrostatic model with a vertical transformed coordinate to improve the resolution in the lower level is designed to study gravety-current vividly.The results indicated that the nonhydrostatic model provided a successful simulation of the gracity-current,especially in the neutrally stable case.The simulated high head with large vertical velocity of gravity-current, the large velocity of underrun and the dense isentropes in the front are closely consistent with those observed.The speed of gravitycurrent in the model is compared with analytical solution (Benjamin.1968).When the orography is included in the model. gravity-current is greatly retarded on the upwind side of the mountain.Conssquently, the gravity-current head in the orography case is much higher than the no-mountain case.An additional bore is triggered and propagates to the upstream direction.As the gravity-current passes over the mountain,its head becomes lower and the gradient of isentropes in front becomes weaken.The differences between hydrostatic and nonhydrostatic simulations are also analyzed.