A numerical model is presented for calculating the changes in sealevel that occur when ice and water masses are rearranged on the surface of elastic and viscoelastic non-rotating Earth. The method is used to calcualte the instantaneous elastic and delayed viscoelastic sea level changes following the partial melting of late Quaternary ice sheets. Suppose we extract two masses M1 and M2, representing two ice sheets from the ocean (it caused a uniform fall 100m in sea level ) , and locate M1 and M2 as two spherical caps in the north pole and the south pole.They can make the core move 22.9m and caused the maximal differentia 23m.