The present invention discloses a coupled waveguide-surface plasmon resonance biosensor, comprising: a grating layer formed of a transparent material, the grating layer comprising a first periodic grating structure; a waveguide layer formed on the first periodic grating structure, the refractive index of the waveguide layer being larger than the refractive index of the grating layer; a plasmon resonance layer formed on the waveguide layer, capable of being optically excited to cause a plasmon resonance wave; and a ligand layer formed on the plasmon resonance layer; capable of being bound to react with receptors of a sample to be tested.