Photomultiplication structure that introduces a small proportion of C60(［60］Fullerene) as electron traps into P3HT(Poly(3-hexylthiophene))∶PC61BM(［6,6］-Phenyl-C61-butyric acid methyl ester) was applied to organic photodetectors. The photomultiplication mechanism based on trap assisted hole tunneling injection and the role of C60 concentration on device photoelectric performances were investigated. When the C60 doping concentration was 1.5wt.%, the resulting photodetector exhibits a 436.4% external quantum efficiency, a 1.62 A·W－1 responsivity, a 2.21×1013Jones detectivity and about 100 dB linear dynamic range at －0.5 V under 455 nm (0.21 mW·cm－2) illumination. The advantage of bulk heterojunction photodetectors that can operate under low bias, combined with the cathode hole tunneling injection which originates from some photoinduced electrons trapped in the active layer especially for the accumulation of electrons near the cathode, was utilized to improve light current dramatically. Thus the photodetector with high detectivity and low operating voltage was obtained.