The photoelectric composites of poly （2，5-dibutyloxy-1，4-phenylene vinylene）/ multi-walled carbon nanotubes （PDBOPV/MWCNTs） were prepared by in-situ polymerization. The results of Fourier transform infrared spectroscopy and Raman spectroscopy indicate that PDBOPV is coated on the surface of MWCNTs. The dimensions of the composite were observed by high resolution transmission electron microscopy，the diameter of PDBOPV/MWCNTs was measured to be about 35—45 nm，and the thickness of the coated PDBOPV is about 15 nm. The absorption of PDBOPV/MWCNTs is strengthened with the contents of MWCNTs increasing，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 PDBOPV/MWCNTs is blue-shifted and intensity of photoluminescence decreases with increasing MWCNTs concentration. PDBOPV/MWCNTs show fluorescence quenching，which involves the inter-molecular photo-induced charge transfer process. The optical band gap of PDBOPV/MWCNTs decreases gradually with the contents of MWCNTs increasing. Third-order optical nonlinear susceptibility of PDBOPV/MWCNT composites were measured by degenerate four wave mixing. The results showed that the third-order nonlinear optical responses of PDBOPV/MWCNT composites were enhanced gradually when MWCNT content increased，which can be attributed to inter-molecular photo-induced electron transfer and π-π electron coupling between PDBOPV and MWCNTs.