The arranging state and second-order nonlinear optical properties of sandwich terbium bisphthalocyanine (TbPcPc*) molecule in Langmuir films and Langmuir-Blodgett (LB) films were investigated by using the surface pressure-area (π～A) isotherm and second harmonic generation method. The mechanisms of nonlinearity were discussed. The experimental results indicate that the TbPcPc* molecules form well-ordered stable monolayer films on interface of water/air, and the TbPcPc* molecules take the face to face orientation for the macrocycles and edge-on configuration in Langmuir films. The dependence of second harmonic generation intensity on the incident angle of fundamental beam was measured. The second harmonic generation signal intensity is very strong and its maximum is obtained at the incident angle of 55°. The second order nonlinear optical susceptibility χ(2) is about 1.64×10-8(esu) and the hyperpolarizability β is about 6.21×10-30(esu). The origin of second harmonic generation is attributed to the electric quadrupole mechanism and the electric dipole mechanism for TbPcPc* molecule.