The mutual coupling of ultralow sidelobe dipole phased arrays is carefully investigated in this paper. A method obtaining the mutual impedances between elements of dipole arrays is first presented by use of network definition. The compensation for mutual coupling using mutual impedances obtained here is discussed. The calculation results show that this compensation method is valid. The effect of mutual coupling upon current distribution on elements of arrays and upon the sidelobe level is also discussed in this paper. These provide theoretical basis for realizing ultralow sidelobe phased arrays.