Recently, new types of nanostructured surface plasmon resonance sensors (SPR) are developing rapidly, and have a wide application prospect. However, most sensors face the disadvantages of low sensitivity or complex structure, which raise the problems that are not able to detect precisely or cost high price to produce. In this work, we proposed a new type of gold-silicon (Au-Si) nanograting structured SPR sensor, which takes the advantages of characteristics of transmission spectrum easier to detect and mass production. The most importantly, it has relatively high sensitivity compared to the commercial sensors. The structure is also incorporated a microfluidic channel as a slot cavity with Silicon dioxide (SiO2) cap. In the case of vertical incidence of light, the analyte in the Microfluid cavity will has a high transmission peak in the near infrared band (near the wavelength of 1500nm actually), which will significantly move when the reflective index(RI) of the analyte changes. The electromagnetic fields of the structure is greatly concentrated in the area of the cavity, which contributes to the high sensitivity up to 1063nm/RIU, which refers to the ratio of the change of the movement of the transmission peak to the change of the RI of the analyte. This structure was simple enough to produce on a large scale easily with low price, and easy to detect due to the concentration on the transmission peak, which make it to be a new type of surface plasmon sensor.