The frequency-dependent hyperpolarizabilities of chelidamic acid complexes M m (C 7 H 3 O 5 N) n (M＝Cu, Ag) were investigated under the time dependent density functional theory (TDDFT) combined with the sum-over-states method (SOS). The relationship between molecular orbitals and nonlinear optical (NLO) properties has been explored. The results show that the charge transitions of π-π* and 3d M -  π* are very important to the second-order polarizabilities, and the largest component of dynamic β is 3.84×10 -25 cm 5 •esu -1 at 0.74 eV for Ag 2 Cu 2 (C 7 H 3 O 5 N) 4 .The charge transition between π-π* is also highly crucial to the third-order polarizabilities, and the largest component of dynamic γ is -4.46×10 -29 esu at 0.50 eV for Ag 2 Cu 2 (C 7 H 3 O 5 N) 4 . The central Cu ion, as electron bridge, extends the range of delocalization and leads to an interesting phenomenon of spiroconjugation.