Abstract: To explore the influence of molecular structures on the nonlinear optical property, the third-order nonlinear optical property of three organometallic complexes with different central metallic atoms (Ni, Cu, and Pd) was investigated by means of z-scan technique. After comparing the nonlinear refractive indexes and the excited state absorption cross-sections of the complexes, it was found that the heavy central metallic atom enhanced the third-order optical property obviously, but the resonant absorption did not have much effect on the nonlinear optical property. The experiment results show that all the three complexes have self focusing and reverse saturation absorption characteristics.