The photoelectric nano-composites of poly(2-methoxy-5-octyloxy)-p-phenylene vinylene/Y2O3:Eu3+ (PMOCOPV/Y2O3:Eu3+) were prepared by dehydrochlorination in-situ polymerization. The result of Fourier transform infrared spectroscopy indicates that PMOCOPV is coated on the surface of Y2O3:Eu3+. Compared with PMOCOPV,the absorption of PMOCOPV/Y2O3:Eu3+ is strengthened,and a red shift of the absorption peak can be clearly observed in the UV-Vis spectrum. Photoluminescence spectroscopy indicates that the maximum emission wavelength of the PMOCOPV/Y2O3:Eu3+ is red-shifted and the intensity of photoluminescence increases in comparison with PMOCOPV. PMOCOPV/Y2O3:Eu3+ shows fluorescence increasing,which involved the inter-molecular photo-induced charge transfer process. The optical band gap of PMOCOPV/Y2O3:Eu3+ decreases. The third-order optical nonlinear susceptibility of PMOCOPV/Y2O3:Eu3+ nano-composites was measured by degenerate four wave mixing. The results show that the third-order nonlinear optical responses of PMOCOPV/Y2O3:Eu3+ nano-composites are enhanced in comparison with PMOCOPV,which can be attributed to inter-molecular photo-induced electron transfer and delocalized π electron coupling between PMOCOPV and Y2O3:Eu3+.