In this work, inverted organic thin film solar cells on grating-structured electrode were fabricated by a nanoimprinting technique. First, a TiO₂ layer was deposited on an ITO/glass slide substrate. Then, the blend of poly(3-hexylthiophene-2,5-diyl) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) with mass ratio of 1:0.8 dissolved in 1,2-dichlorobenzene was spin-coated on the TiO₂ layer. The grating pattern was created on the P3HT:PCBM layer by nanoimprinting technique using PDMS stamp. PDMS grating pattern template was created also by nanoimprinting using DVD-R grating template with the grating pitch of 740 nm. Poly(3,4ethylenedioxythiophene):poly(styrene sulfonate) (PEDOS:PSS) was then spin-coated on the patterned PHT:PCBM layer. Finally, Au was deposited on the PEDOT:PSS as a top electrode by vacuum evaporation technique. The fabricated device showed higher short-circuit photo-current as compared to standard flat solar cells. Transmitted-surface plasmon resonance (T-SPR) measurements showed that the surface plasmon excitation is one of the factors for an enhancement of the device performance. Furthermore, polarized UV-vis. absorption measurements exhibited that the P3HT molecules aligned in vertical direction (in-plane) to the grating groove direction after the nanoimprinting.