In this study, two-dimensional photonic crystal (PhC) was developed using functionalized polymers and nanoimprint lithography (NIL) for biosensing applications. In addition, using functionalized polymer-based PhC, detection of DNA hybridization or potassium ion were successfully applied by changing of PhC design and base material. For detection of DNA hybridization, PhC cavity was fabricated using polymer. By introducing of cavity into PhC, surrounding refractive index change due to the DNA hybridization could be detected high sensitively. Furthermore, for detection of potassium ion, PhC was fabricated using ionophore contained plasticized poly (vinyl chloride) (PVC). By using ionophore contained PVC-based PhC, potassium ion was specifically extracted into the PhC by ionophore. Then, potassium ion could be detected by the optical characteristics change that attributed by the physical and chemical property change of base material. From these result shows that the functionalized polymer-based PhC enables to apply for developing of high sensitive optical biosensor.