Abstract On the basis of the threedimensional(3D) layered models of crustal structures from the 3D forward simulation of gravity in Tibetan plateau and by use of the software of IGMAS the geoidal undulations caused by the inhomogeneity of threedimensional crustal structures in Tibetan plateau are simulated. The study shows that, the geoid in middleshort wavelength is produced by the inhomogeneity of density between each layer within the crust in Tibetan plateau, it means that the interface undulation is the main mechanism of geoid in middleshort wavelength. For each layer, the main reason of geoid changing in middlehigh frequency is the material inhomogeneity between lower crust and upper mantle, secondly, is the inhomogeneity between middle crust and lower crust, the influence of inhomogeneity between upper crust and middle crust on geoid is less. The material inhomogeneity because of the low velocity layer has a great effect on geoid.On the basis of the threedimensional(3D) layered models of crustal structures from the 3D forward simulation of gravity in Tibetan plateau and by use of the software of IGMAS the geoidal undulations caused by the inhomogeneity of threedimensional crustal structures in Tibetan plateau are simulated. The study shows that, the geoid in middleshort wavelength is produced by the inhomogeneity of density between each layer within the crust in Tibetan plateau, it means that the interface undulation is the main mechanism of geoid in middleshort wavelength. For each layer, the main reason of geoid changing in middlehigh frequency is the material inhomogeneity between lower crust and upper mantle, secondly, is the inhomogeneity between middle crust and lower crust, the influence of inhomogeneity between upper crust and middle crust on geoid is less. The material inhomogeneity because of the low velocity layer has a great effect on geoid.
