The present invention provides a surface plasmon resonance (SPR) unit having at least one microfluidic channel with grating structures embedded in so that a grating-coupled surface plasmon resonance can be induced by an incident light while fluid in the microfluidic channel contacts or flows through the grating area. The induced variation of optical signal due to the SPR effect is analyzed for performing bio-screening and assay of bioaffinity reaction. Meanwhile, present invention further provides an SPR inspection system possessing a rotation power to the SPR unit such that the SPR unit is capable of rotating and thereby generating a centrifugal force for driving the flow inside the microfluidic channels so as to achieve the label-free and high throughput SPR inspection system with low-cost.