The Au-SiO2-Si thin film MIS(Metal-Insulator-Semiconductor)tunnel junction was fabricated.The light emission property and I-V characteristic of this junction were measured and analyzed.Result indicated that the light emission was due to the excitation of Surface Plasmon Polariton(SPP)and the couple of SPP with the surface roughness subsequently in the MIS system.We observed the negative resistance phenomenon(NRP) in the I-V curve of this MIS junction,which was explained by the electrons bonding model. We also got the AFM(atomic force microscopy)photo of the surface of MIS junction, by which the relation among the electrons tunneling, the excitation of SPP,and the light emission of the MIS junction was discussed.