A miniaturized metal semiconductor metal photodetector was developed as the core detector for chemiluminescence biosensor. The biosensor utilized the semiconductor manufacturing to fabricate the 83 interdigitated patterns of 250-nm metal line and 278-nm space in 100 mu m x 100 mu m active region. The established real-time detector was operated at 0.4 V to ensure the maximal signal to background ratio of 3600 under illumination intensity of 1.46 mW/cm(2). A chemiluminescence in the miniaturized chamber was successfully proposed to determine the model protein concentration in real-time analysis. Before the emission of light from the catalytic reaction of substrate, the model protein of streptavidin bound to horseradish peroxidase was successfully immobilized onto the sensor surface through the high-affinity conjugate with biotin. The detection limit of 4.76 nM for streptavidin analysis was obtained under the calibration curve of linear range over 5-100 nM with correlation coefficient of 0.9999.