Tetraphenylporphyrin (TPP) and its nickel(II) (NiTPP) complex have been synthesized, their crystal structures have been determined by means of X-ray single crystal diffraction. The TPP possesses good planarity in the porphyrin core, while in the complex the planarity disappeared. The central nickel(II) ion coordinates with four nitrogen atoms, which constructed a distorted square environment. Their third-order nonlinear optical properties have been studied using Z-scan technique at wavelength 532nm and 1064nm in picosecond (ps) domain. At 532nm nonlinear absorption were observed, TPP shows two-photon absorption (TPA) combined with saturable absorption (SA), while NiTPP shows SA. At 1064nm nonlinear refraction were observed, the molecular second hyperpolarizability gamma of the NiTPP was about 1.4times larger than that of the TPP.