This paper reports the fabrication, testing and characterization of an optofluidic sensor for biological sample detection at nanoscale. This biosensor consists of a two-layer structure fabricated by micro- and nanofabrication technology. A microchannel and its fluid connections have been patterned and formed in the silicon and glass. Gold nanoparticles have been fabricated by nanosphere lithography (NSL) on glass. The device has been tested and characterized by localized surface plasmon resonance (LSPR) experiment using a UV/vis spectrometer to obtain the absorbance as a function of wavelength. This device has innovatively integrated microfluidic and plasmonic technology in chip-level and the testing results show that the sensitivity is very high and suitable for biosensing. This device exhibits great potentials to yield ultra-sensitive bio-detection and precise control of ultra-small amount of bio-fluids.