Iranian plateau is one of the most complex tectonic areas in the world. Remnants of the Neotethys Ocean slab, process of continent-continent collision in the mantle and the difference in the timing of slab-breakoff and collision in this area yield a complex system in the upper and lower mantle. For determination of structures in this area we present a 3D teleseismic tomography. We first propose a method for inverting five seismic networks simultaneously. For correcting the traveltimes data we calculate the receiver function on three temporary networks. Then we perform a checkerboard test for finding the best resolved part of our model. We try to find the slab remnants of the Neotethys Ocean underneath the western, middle and eastern parts of Iranian plateau.