High integration density, high responsivity, bandgap limitation breaking and multifunctional silicon photodetectors are the long term goals in the field of light detection. The photothermoelectric (PTE) effect discovered in silicon nanostructures utilizes the photon-induced temperature gradient to achieve electrical detection and provides a promising way towards meeting the above requirements. Here we report a plasmon modulated silicon nanostripe PTE detector with an open-circuit photovoltage responsivity of ∼82 mV μW-1. The gold subwavelength nanogratings provide enhanced optical absorption and polarization and wavelength sensitivity. An interesting reversed Seebeck coefficient of silicon caused by the Cr/Au contact was observed. This plasmon enhanced silicon PTE effect would pave the way for high integration, CMOS compatible photodetection and light harvesting devices.