The lighttrapping was studied by using Au nanoparticles (NPs) to create localized surface plasmons resonance (LSPR) effect on the surface of polycrystalline silicon thin film solar cells (PSTFSC). The random arrays of selfassembled Au NPs were decorated onto the surface of PSTFSCs with the aid of magnetron sputtering. By modulating the magnetron sputtering time for the Au film thickness, the size of Au NPs can be manipulated. The UVvis absorption spectra show that the photoresponse of asprepared samples is extended from 400 to 800nm, which is ascribed to the excitation of LSPR. Furthermore, a distinct redshift of LSPR absorption peak with the increase of Au NPs size was observed. Meanwhile, the local electromagnetic (EM) field efficiency enhancement is shown to be caused by plasmonically enhanced noble metalNPs, which was confirmed by surfaceenhanced Raman spectroscopy (SERS). Moreover, a significant photoelectric conversion efficiency (PCE) of 14.8% for PSTFSC decorated with Au NPs sputtering time of 50s is obtained compared with that of 10.4% for the pristine PSTFSC, which is shown by the current densityvoltage (JV) characteristics measurement.