Photodetectors are generally the most promising, representative and widely-used type of detectors, and the applications of photodetectors are quite extensively. Photodetectors are made of photosensitive elements which are able to turn the light signal into electrical signal. Owing to the nature of fast responding speed and capability of large volume manufacturing, it provides photodetectors an advantageous future in biomedical sensing territory. This study focuses on fabrication method of the flexible photodetectors and application to biomolecule sensing through luminescence. The photosensitive element is based on silicon wafer which is treated with chemical etching process to achieve pliable characteristic. Then, the metal-semiconductor-metal structural flexible photodetectors are achieved after integrated with simple fabricating processes. The accomplished devices are handled with immobilization steps to fix the target enzyme which is able to catalyze the luminescent reaction. We provide a portable biomolecule sensor with outstanding flexible characteristic and high sensitivity and it exhibits illustrious stable consequence in various situations.