The present invention provides a biosensor and an application of the same. The biosensor includes a substrate, a first polymer layer and a second polymer layer. The first polymer layer includes composite antibodies, each of which includes a first antibody and a labelling molecule. The second polymer layer has an inverse opal photonic crystal structure where gold nanoparticles and second antibodies are distributed. At least one of the composite antibodies, an antigen and at least one of the second antibodies forms a complex in the second polymer layer, and an antigen concentration is obtained by a fluorescence intensity, a degree of red-shift or a change in a visual color of the biosensor.
