Using the NCAR nonhydrostatic mesoscale model MM5V3.5 and through triple nested technique, the idealized circular oasis terrain was designed, the circulation and boundary layer character in oasis were simulated.It is found that the sensitive heat flux in oasis changes with terrain elevation, but the latent heat flux doesn't change with terrain elevation, which is related to the characteristic of underlying surface in oasis.The sensitive heat flux in oasis is small and the latent heat flux is large, climatic effect in oasis is obvious.The circulation in oasis is consistent with terrain ones, but the intensity of terrain circulation is weaker than that of in oasis.The influence of oasis on humidity profile of boundary layer is obvious.The water vapour transport in oasis is enhanced through downdraft in terrain, making the climatic effect in oasis of mountain valley to enhance as well.The result showed that the climatic effect in oasis is enhanced because the terrain circulation is consistent with oasis ones.