The invention discloses a poling method for a relaxor ferroelectric single crystal as a nonlinear optical material. The method comprises an annealing process and a polarization process; the relaxor ferroelectric single crystal comprises a binary (1-x)Pb(Mg1/3Nb2/3)O(3-x)PbTiO3 system and a ternary (1-x-y)Pb(In1/2Nb1/2)O(3-x)Pb(Mg1/3Nb2/3)O(3-y)PbTiO3 system; according to the annealing process, the relaxor ferroelectric single crystal after grinding and polishing is subjected to annealing treatment in atmosphere, stress caused by machining is removed, and spontaneous strain produced in a ferroelectric phase forming process is released to the great degree through quite slow cooling, so that the probability of cracking caused by electrically induced domain rotation in the crystal poling process is reduced. Besides, after an electric field is removed, a remaining depolarization field can be induced to form a nanometer domain structure. In order to guarantee formation and stability of a single-domain structure, the remaining depolarization field can be compensated by bulk shielding effect formed through electrode injection, the relaxor ferroelectric single crystal with high poling performance and stable performance is obtained, and the material has the characteristics of small half-wave voltage, large photo damage threshold, large electro-optic coefficient and the like and is far better than BBO, KTP, LN and other materials.