A high detectivity organic photodetector with active layer P3HT:PBDT-TT-C∶PC61BM covering the visible wavelength range was prepared by solution spin coating and high vacuum evaporation. The effects of PBDT-TT-C doping P3HT∶PC61BM on the optical properties of the active layer films were investigated by atomic force microscopy, UV-visible absorption spectroscopy and fluorescence spectroscopy. It was found that when the mass ratio of P3HT∶PBDT-TT-C∶PC61BM in the active layer was 8∶2∶10, the response spectrum of the active layer was broadened to 350~780 nm. The optical responsiveness and external quantum efficiency of the red, green and blue primary colors of the detector under the bias of －1 V reached 422 mA/W, 464 mA/W, 286 mA/W and 83%, 108%, 77%, respectively, and the specific detectivity reached above 1012 Jones. The results show that the organic material with an organic material complementary is doped. On the basis of ensuring the microscopic morphology of the film, By adjusting the mass ratio of the ternary mixed material, not only the carrier generation and transport can be optimized, the photocurrent of the device is improved, but also the crystallization of the thin film can be promoted by the incorporation of the third component, and the dark current of the device can be reduced.